The Experts below are selected from a list of 19374 Experts worldwide ranked by ideXlab platform

Teizo Kitagawa - One of the best experts on this subject based on the ideXlab platform.

  • Heterogeneity between Two α Subunits of α2β2 HuMan HeMoglobin and O2 Binding Properties: RaMan, 1H Nuclear Magnetic Resonance, and Terahertz Spectra
    Biochemistry, 2017
    Co-Authors: Shigenori Nagatomo, Teizo Kitagawa, Kazuya Saito, Kohji Yamamoto, Takashi Ogura, Masako Nagai
    Abstract:

    Following a previous detailed investigation of the β subunit of α2β2 huMan adult HeMoglobin (Hb A), this study focuses on the α subunit by using three natural valency hybrid α(Fe2+-deoxy/O2)β(Fe3+) HeMoglobin M (Hb M) in which O2 cannot bind to the β subunit: Hb M Hyde Park (β92His → Tyr), Hb M Saskatoon (β63His → Tyr), and Hb M Milwaukee (β67Val → Glu). In contrast with the β subunit that exhibited a clear correlation between O2 affinity and Fe2+–His stretching frequencies, the Fe2+–His stretching Mode of the α subunit gave two RaMan bands only in the T quaternary structure. This Means the presence of two tertiary structures in α subunits of the α2β2 tetraMer with T structure, and the two structures seeMed to be nondynaMical as judged froM terahertz absorption spectra in the 5–30 cM–1 region of Hb M Milwaukee, α(Fe2+-deoxy)β(Fe3+). This kind of heterogeneity of α subunits was noticed in the reported spectra of a Metal hybrid Hb A like α(Fe2+-deoxy)β(Co2+) and, therefore, seeMs to be universal aMong α sub...

  • Differences in coordination states of substituted tyrosine residues and quaternary structures aMong HeMoglobin M probed by resonance RaMan spectroscopy
    JBIC Journal of Biological Inorganic Chemistry, 2010
    Co-Authors: Yayoi Aki, Kiyohiro Imai, Masako Nagai, Yukifumi Nagai, Shigenori Nagatomo, Michihiko Aki, Akira Sato, Minoru Kubo, Teizo Kitagawa
    Abstract:

    AMong the four types of HeMoglobin (Hb) M with a substitution of a tyrosine (Tyr) for either the proxiMal (F8) or distal (E7) histidine in the α or β subunits, only Hb M Saskatoon (βE7Tyr) assuMes a hexacoordinate structure and its abnorMal subunits can be reduced readily by MetHeMoglobin (MetHb) reductase. This is distinct froM the other three M Hbs. To gain new insight into the cause of the difference, we exaMined the ionization states of E7 and F8 Tyrs by UV resonance RaMan (RR) spectroscopy and Fe–O(Tyr) bonding by visible RR spectroscopy. Hb M Iwate (αF8Tyr), Hb M Boston (αE7Tyr), and Hb M Hyde Park (βF8Tyr) exhibited two extra UV RR bands at 1,603 cM^−1 (Y8a′) and 1,167 cM^−1 (Y9a′) arising froM deprotonated (ionized) Tyr, but Hb M Saskatoon displayed the UV RR bands of protonated (unionized) Tyr at 1,620 and 1,175 cM^−1 in addition to those of deprotonated Tyr. Evidence for the bonding of both ionization states of Tyr to the heMe in Hb M Saskatoon was provided by visible RR spectroscopy. These results indicate that βE7Tyr of Hb M Saskatoon is in equilibriuM between protonated and deprotonated forMs, which is responsible for facile reducibility. CoMparison of the UV RR spectral features of MetHb M with that of MetHb A has revealed that MetHb M Saskatoon and MetHb M Hyde Park are in the R (relaxed) structure, siMilar to that of MetHb A, whereas MetHb M Iwate, MetHb M Boston and MetHb M Milwaukee are in the T (tense) quaternary structure.

  • HeMe structures of five variants of HeMoglobin M probed by resonance RaMan spectroscopy.
    Biochemistry, 2004
    Co-Authors: Y. Jin, Masako Nagai, Yukifumi Nagai, Shigenori Nagatomo, Teizo Kitagawa
    Abstract:

    The alpha-abnorMal HeMoglobin (Hb) M variants show physiological properties different froM the beta-abnorMal Hb M variants, that is, extreMely low oxygen affinity of the norMal subunit and extraordinary resistance to both enzyMatic and cheMical reduction of the abnorMal Met-subunit. To get insight into the contribution of heMe structures to these differences aMong Hb M's, we exaMined the 406.7-nM excited resonance RaMan (RR) spectra of five Hb M's in the frequency region froM 1700 to 200 cM(-1). In the high-frequency region, profound differences between Met-alpha and Met-beta abnorMal subunits were observed for the in-plane skeletal Modes (the nu(C=C), nu(37), nu(2), nu(11), and nu(38) bands), probably reflecting different distortions of heMe structure caused by the out-of-plane displaceMent of the heMe iron due to tyrosine coordination. Below 900 cM(-1), Hb M Iwate [alpha(F8)His --> Tyr] exhibited a distinct spectral pattern for nu(15), gaMMa(11), delta(C(beta)C(a)C(b))(2,4), and delta(C(beta)C(c)C(d))(6,7) coMpared to that of Hb M Boston [alpha(E7)His --> Tyr], although both heMe irons are coordinated by Tyr. The beta-abnorMal Hb M variants, naMely, Hb M Hyde Park [beta(F8)His --> Tyr], Hb M Saskatoon [beta(E7)His --> Tyr], and Hb M Milwaukee [beta(E11)Val --> Glu], displayed RR band patterns siMilar to that of MetHb A, but with soMe Minor individual differences. The RR bands characteristic of the Met-subunits of Hb M's totally disappeared by cheMical reduction, and the ferrous heMe of abnorMal subunits was no longer bonded with Tyr or Glu. They were bonded to the distal (E7) or proxiMal (F8) His, and this was confirMed by the presence of the nu(Fe-His) Mode at 215 cM(-1) in the 441.6-nM excited RR spectra. A possible involveMent of heMe distortion in differences of reducibility of abnorMal subunits and oxygen affinity of norMal subunits is discussed.

  • HeMe structure of HeMoglobin M Iwate [alpha 87(F8)His-->Tyr]: a UV and visible resonance RaMan study.
    Biochemistry, 2000
    Co-Authors: Masako Nagai, Y. Jin, Shigenori Nagatomo, Michihiko Aki, H Sakai, Teizo Kitagawa
    Abstract:

    HeMe structures of a natural Mutant HeMoglobin (Hb), Hb M Iwate [alpha87(F8)His-->Tyr], and protonation of its F8-Tyr were exaMined with the 244-nM excited UV resonance RaMan (UVRR) and the 406.7- and 441.6-nM excited visible resonance RaMan (RR) spectroscopy. It was clarified froM the UVRR bands at 1605 and 1166 cM(-)(1) characteristic of tyrosinate that the tyrosine (F8) of the abnorMal subunit in Hb M Iwate adopts a deprotonated forM. UV RaMan bands of other Tyr residues indicated that the protein takes the T-quaternary structure even in the Met forM. Although both heMes of alpha and beta subunits in MetHb A take a six-coordinate (6c) high-spin structure, the 406.7-nM excited RR spectruM of MetHb M Iwate indicated that the abnorMal alpha subunit adopts a 5c high-spin structure. The present results and our previous observation of the nu(Fe)(-)(O(tyrosine)) RaMan band [Nagai et al. (1989) BiocheMistry 28, 2418-2422] have proved that F8-tyrosinate is covalently bound to Fe(III) heMe in the alpha subunit of Hb M Iwate. As a result, peripheral groups of porphyrin ring, especially the vinyl and the propionate side chains, were so strongly influenced that the RR spectruM in the low-frequency region excited at 406.7 nM is distinctly changed froM the norMal pattern. When Hb M Iwate was fully reduced, the characteristic UVRR bands of tyrosinate disappeared and the RaMan bands of tyrosine at 1620 (Y8a), 1207 (Y7a), and 1177 cM(-)(1) (Y9a) increased in intensity. Coordination of distal His(E7) to the Fe(II) heMe in the reduced alpha subunit of Hb M Iwate was proved by the observation of the nu(Fe)(-)(His) RR band in the 441.6-nM excited RR spectruM at the saMe frequency as that of its isolated alpha chain. The effects of the distal-His coordination on the heMe appeared as a distortion of the peripheral groups of heMe. A possible MechanisM for the forMation of a Fe(III)-tyrosinate bond in Hb M Iwate is discussed.

  • DeterMination of Fe-CO geoMetry in the subunits of carbonMonoxy HeMoglobin M Boston using feMtosecond infrared spectroscopy.
    Biochemistry, 1993
    Co-Authors: Tianquan Lian, Teizo Kitagawa, B Locke, M. Nagai, R M Hochstrasser
    Abstract:

    We have undertaken ultrafast infrared (IR) spectroscopic studies in order to elucidate the geoMetry of bound CO in the alpha and beta subunits of HeMoglobin (Hb) M Boston 13CO. Hb M Boston is a Mutant huMan Hb in which the distal histidine in the alpha subunits is replaced by a tyrosine. The IR absorptions of bound 13CO fall at 1925 cM-1 for the alpha subunits and 1907 cM-1 for the beta subunits. Despite a difference of nearly 20 cM-1 in these peaks, the Measured anisotropies of the bound 13CO depletions following 30% photolysis are nearly identical, with values of -0.142 +/- 0.002 obtained for the alpha subunits and -0.140 +/- 0.003 obtained for the beta subunits. These translate to values of 20 degrees +/- 1 degree and 21 degrees +/- 1 degree for the values of the average angles between the CO bond and the norMal to the heMe planes in the alpha and beta subunits, respectively. Our present results and the work of previous investigators [Nagai, M., YoneyaMa, Y., & Kitagawa, T. (1991) BiocheMistry 30, 6495-6503] suggest that a change in the polar interactions of the bound CO with the heMe pocket environMent upon substitution of tyrosine for the distal histidine and a less bent structure for the Fe-C-O unit in the alpha subunits are responsible for the difference in the bound CO absorption frequencies in the alpha and beta subunits. A spectruM of the depletion of the bound 13CO peaks following photolysis indicates that both subunits photodissociate CO with the saMe quantuM yield and neither subunit exhibits significant recoMbination within 1 ns.

Masako Nagai - One of the best experts on this subject based on the ideXlab platform.

  • Heterogeneity between Two α Subunits of α2β2 HuMan HeMoglobin and O2 Binding Properties: RaMan, 1H Nuclear Magnetic Resonance, and Terahertz Spectra
    Biochemistry, 2017
    Co-Authors: Shigenori Nagatomo, Teizo Kitagawa, Kazuya Saito, Kohji Yamamoto, Takashi Ogura, Masako Nagai
    Abstract:

    Following a previous detailed investigation of the β subunit of α2β2 huMan adult HeMoglobin (Hb A), this study focuses on the α subunit by using three natural valency hybrid α(Fe2+-deoxy/O2)β(Fe3+) HeMoglobin M (Hb M) in which O2 cannot bind to the β subunit: Hb M Hyde Park (β92His → Tyr), Hb M Saskatoon (β63His → Tyr), and Hb M Milwaukee (β67Val → Glu). In contrast with the β subunit that exhibited a clear correlation between O2 affinity and Fe2+–His stretching frequencies, the Fe2+–His stretching Mode of the α subunit gave two RaMan bands only in the T quaternary structure. This Means the presence of two tertiary structures in α subunits of the α2β2 tetraMer with T structure, and the two structures seeMed to be nondynaMical as judged froM terahertz absorption spectra in the 5–30 cM–1 region of Hb M Milwaukee, α(Fe2+-deoxy)β(Fe3+). This kind of heterogeneity of α subunits was noticed in the reported spectra of a Metal hybrid Hb A like α(Fe2+-deoxy)β(Co2+) and, therefore, seeMs to be universal aMong α sub...

  • Differences in coordination states of substituted tyrosine residues and quaternary structures aMong HeMoglobin M probed by resonance RaMan spectroscopy
    JBIC Journal of Biological Inorganic Chemistry, 2010
    Co-Authors: Yayoi Aki, Kiyohiro Imai, Masako Nagai, Yukifumi Nagai, Shigenori Nagatomo, Michihiko Aki, Akira Sato, Minoru Kubo, Teizo Kitagawa
    Abstract:

    AMong the four types of HeMoglobin (Hb) M with a substitution of a tyrosine (Tyr) for either the proxiMal (F8) or distal (E7) histidine in the α or β subunits, only Hb M Saskatoon (βE7Tyr) assuMes a hexacoordinate structure and its abnorMal subunits can be reduced readily by MetHeMoglobin (MetHb) reductase. This is distinct froM the other three M Hbs. To gain new insight into the cause of the difference, we exaMined the ionization states of E7 and F8 Tyrs by UV resonance RaMan (RR) spectroscopy and Fe–O(Tyr) bonding by visible RR spectroscopy. Hb M Iwate (αF8Tyr), Hb M Boston (αE7Tyr), and Hb M Hyde Park (βF8Tyr) exhibited two extra UV RR bands at 1,603 cM^−1 (Y8a′) and 1,167 cM^−1 (Y9a′) arising froM deprotonated (ionized) Tyr, but Hb M Saskatoon displayed the UV RR bands of protonated (unionized) Tyr at 1,620 and 1,175 cM^−1 in addition to those of deprotonated Tyr. Evidence for the bonding of both ionization states of Tyr to the heMe in Hb M Saskatoon was provided by visible RR spectroscopy. These results indicate that βE7Tyr of Hb M Saskatoon is in equilibriuM between protonated and deprotonated forMs, which is responsible for facile reducibility. CoMparison of the UV RR spectral features of MetHb M with that of MetHb A has revealed that MetHb M Saskatoon and MetHb M Hyde Park are in the R (relaxed) structure, siMilar to that of MetHb A, whereas MetHb M Iwate, MetHb M Boston and MetHb M Milwaukee are in the T (tense) quaternary structure.

  • HeMe structures of five variants of HeMoglobin M probed by resonance RaMan spectroscopy.
    Biochemistry, 2004
    Co-Authors: Y. Jin, Masako Nagai, Yukifumi Nagai, Shigenori Nagatomo, Teizo Kitagawa
    Abstract:

    The alpha-abnorMal HeMoglobin (Hb) M variants show physiological properties different froM the beta-abnorMal Hb M variants, that is, extreMely low oxygen affinity of the norMal subunit and extraordinary resistance to both enzyMatic and cheMical reduction of the abnorMal Met-subunit. To get insight into the contribution of heMe structures to these differences aMong Hb M's, we exaMined the 406.7-nM excited resonance RaMan (RR) spectra of five Hb M's in the frequency region froM 1700 to 200 cM(-1). In the high-frequency region, profound differences between Met-alpha and Met-beta abnorMal subunits were observed for the in-plane skeletal Modes (the nu(C=C), nu(37), nu(2), nu(11), and nu(38) bands), probably reflecting different distortions of heMe structure caused by the out-of-plane displaceMent of the heMe iron due to tyrosine coordination. Below 900 cM(-1), Hb M Iwate [alpha(F8)His --> Tyr] exhibited a distinct spectral pattern for nu(15), gaMMa(11), delta(C(beta)C(a)C(b))(2,4), and delta(C(beta)C(c)C(d))(6,7) coMpared to that of Hb M Boston [alpha(E7)His --> Tyr], although both heMe irons are coordinated by Tyr. The beta-abnorMal Hb M variants, naMely, Hb M Hyde Park [beta(F8)His --> Tyr], Hb M Saskatoon [beta(E7)His --> Tyr], and Hb M Milwaukee [beta(E11)Val --> Glu], displayed RR band patterns siMilar to that of MetHb A, but with soMe Minor individual differences. The RR bands characteristic of the Met-subunits of Hb M's totally disappeared by cheMical reduction, and the ferrous heMe of abnorMal subunits was no longer bonded with Tyr or Glu. They were bonded to the distal (E7) or proxiMal (F8) His, and this was confirMed by the presence of the nu(Fe-His) Mode at 215 cM(-1) in the 441.6-nM excited RR spectra. A possible involveMent of heMe distortion in differences of reducibility of abnorMal subunits and oxygen affinity of norMal subunits is discussed.

  • HeMe structure of HeMoglobin M Iwate [alpha 87(F8)His-->Tyr]: a UV and visible resonance RaMan study.
    Biochemistry, 2000
    Co-Authors: Masako Nagai, Y. Jin, Shigenori Nagatomo, Michihiko Aki, H Sakai, Teizo Kitagawa
    Abstract:

    HeMe structures of a natural Mutant HeMoglobin (Hb), Hb M Iwate [alpha87(F8)His-->Tyr], and protonation of its F8-Tyr were exaMined with the 244-nM excited UV resonance RaMan (UVRR) and the 406.7- and 441.6-nM excited visible resonance RaMan (RR) spectroscopy. It was clarified froM the UVRR bands at 1605 and 1166 cM(-)(1) characteristic of tyrosinate that the tyrosine (F8) of the abnorMal subunit in Hb M Iwate adopts a deprotonated forM. UV RaMan bands of other Tyr residues indicated that the protein takes the T-quaternary structure even in the Met forM. Although both heMes of alpha and beta subunits in MetHb A take a six-coordinate (6c) high-spin structure, the 406.7-nM excited RR spectruM of MetHb M Iwate indicated that the abnorMal alpha subunit adopts a 5c high-spin structure. The present results and our previous observation of the nu(Fe)(-)(O(tyrosine)) RaMan band [Nagai et al. (1989) BiocheMistry 28, 2418-2422] have proved that F8-tyrosinate is covalently bound to Fe(III) heMe in the alpha subunit of Hb M Iwate. As a result, peripheral groups of porphyrin ring, especially the vinyl and the propionate side chains, were so strongly influenced that the RR spectruM in the low-frequency region excited at 406.7 nM is distinctly changed froM the norMal pattern. When Hb M Iwate was fully reduced, the characteristic UVRR bands of tyrosinate disappeared and the RaMan bands of tyrosine at 1620 (Y8a), 1207 (Y7a), and 1177 cM(-)(1) (Y9a) increased in intensity. Coordination of distal His(E7) to the Fe(II) heMe in the reduced alpha subunit of Hb M Iwate was proved by the observation of the nu(Fe)(-)(His) RR band in the 441.6-nM excited RR spectruM at the saMe frequency as that of its isolated alpha chain. The effects of the distal-His coordination on the heMe appeared as a distortion of the peripheral groups of heMe. A possible MechanisM for the forMation of a Fe(III)-tyrosinate bond in Hb M Iwate is discussed.

  • Studies of the oxidation states of HeMoglobin M Boston and HeMoglobin M Saskatoon in blood by EPR spectroscopy.
    Biochemical and biophysical research communications, 1995
    Co-Authors: Masako Nagai, Yoshimasa Yoneyama, Kazuhiro Mawatari, Y. Nagai, S. Horita, H. Hori
    Abstract:

    Abstract The extent of the oxidation of HeMoglobin (Hb) M Saskatoon (β63His → Tyr) and Hb M Boston (α58His → Tyr) in the patient′s blood was deterMined by MeasureMent of the intensity of EPR signals at g ⊥ =6.0 for the norMal subunits, g 1 =6.7 for the Mutant subunits of Hb M Saskatoon and g 1 =6.3 for those of Hb M Boston, respectively. The aMounts of reduced Mutant subunits were estiMated froM the EPR signal intensities and the aMounts of Hb present as Mutant Hb in the blood. About 50% and 76% of Mutant subunits in Hb M Boston and Hb M Saskatoon reMained reduced in the fresh blood. Gentle shaking of the blood at 37°C for 15 hours in air brought about autoxidation of the norMal subunits as well as the Mutant subunits of the two Hbs M, indicating that the presence of the Mutant subunits facilitated autoxidation of the norMal subunits. Possible involveMent of NADH-MetHb reductase in erythrocytes in Maintenance of the reduced Mutant subunits of Hb M Saskatoon was discussed.

Shigenori Nagatomo - One of the best experts on this subject based on the ideXlab platform.

  • Heterogeneity between Two α Subunits of α2β2 HuMan HeMoglobin and O2 Binding Properties: RaMan, 1H Nuclear Magnetic Resonance, and Terahertz Spectra
    Biochemistry, 2017
    Co-Authors: Shigenori Nagatomo, Teizo Kitagawa, Kazuya Saito, Kohji Yamamoto, Takashi Ogura, Masako Nagai
    Abstract:

    Following a previous detailed investigation of the β subunit of α2β2 huMan adult HeMoglobin (Hb A), this study focuses on the α subunit by using three natural valency hybrid α(Fe2+-deoxy/O2)β(Fe3+) HeMoglobin M (Hb M) in which O2 cannot bind to the β subunit: Hb M Hyde Park (β92His → Tyr), Hb M Saskatoon (β63His → Tyr), and Hb M Milwaukee (β67Val → Glu). In contrast with the β subunit that exhibited a clear correlation between O2 affinity and Fe2+–His stretching frequencies, the Fe2+–His stretching Mode of the α subunit gave two RaMan bands only in the T quaternary structure. This Means the presence of two tertiary structures in α subunits of the α2β2 tetraMer with T structure, and the two structures seeMed to be nondynaMical as judged froM terahertz absorption spectra in the 5–30 cM–1 region of Hb M Milwaukee, α(Fe2+-deoxy)β(Fe3+). This kind of heterogeneity of α subunits was noticed in the reported spectra of a Metal hybrid Hb A like α(Fe2+-deoxy)β(Co2+) and, therefore, seeMs to be universal aMong α sub...

  • Differences in coordination states of substituted tyrosine residues and quaternary structures aMong HeMoglobin M probed by resonance RaMan spectroscopy
    JBIC Journal of Biological Inorganic Chemistry, 2010
    Co-Authors: Yayoi Aki, Kiyohiro Imai, Masako Nagai, Yukifumi Nagai, Shigenori Nagatomo, Michihiko Aki, Akira Sato, Minoru Kubo, Teizo Kitagawa
    Abstract:

    AMong the four types of HeMoglobin (Hb) M with a substitution of a tyrosine (Tyr) for either the proxiMal (F8) or distal (E7) histidine in the α or β subunits, only Hb M Saskatoon (βE7Tyr) assuMes a hexacoordinate structure and its abnorMal subunits can be reduced readily by MetHeMoglobin (MetHb) reductase. This is distinct froM the other three M Hbs. To gain new insight into the cause of the difference, we exaMined the ionization states of E7 and F8 Tyrs by UV resonance RaMan (RR) spectroscopy and Fe–O(Tyr) bonding by visible RR spectroscopy. Hb M Iwate (αF8Tyr), Hb M Boston (αE7Tyr), and Hb M Hyde Park (βF8Tyr) exhibited two extra UV RR bands at 1,603 cM^−1 (Y8a′) and 1,167 cM^−1 (Y9a′) arising froM deprotonated (ionized) Tyr, but Hb M Saskatoon displayed the UV RR bands of protonated (unionized) Tyr at 1,620 and 1,175 cM^−1 in addition to those of deprotonated Tyr. Evidence for the bonding of both ionization states of Tyr to the heMe in Hb M Saskatoon was provided by visible RR spectroscopy. These results indicate that βE7Tyr of Hb M Saskatoon is in equilibriuM between protonated and deprotonated forMs, which is responsible for facile reducibility. CoMparison of the UV RR spectral features of MetHb M with that of MetHb A has revealed that MetHb M Saskatoon and MetHb M Hyde Park are in the R (relaxed) structure, siMilar to that of MetHb A, whereas MetHb M Iwate, MetHb M Boston and MetHb M Milwaukee are in the T (tense) quaternary structure.

  • HeMe structures of five variants of HeMoglobin M probed by resonance RaMan spectroscopy.
    Biochemistry, 2004
    Co-Authors: Y. Jin, Masako Nagai, Yukifumi Nagai, Shigenori Nagatomo, Teizo Kitagawa
    Abstract:

    The alpha-abnorMal HeMoglobin (Hb) M variants show physiological properties different froM the beta-abnorMal Hb M variants, that is, extreMely low oxygen affinity of the norMal subunit and extraordinary resistance to both enzyMatic and cheMical reduction of the abnorMal Met-subunit. To get insight into the contribution of heMe structures to these differences aMong Hb M's, we exaMined the 406.7-nM excited resonance RaMan (RR) spectra of five Hb M's in the frequency region froM 1700 to 200 cM(-1). In the high-frequency region, profound differences between Met-alpha and Met-beta abnorMal subunits were observed for the in-plane skeletal Modes (the nu(C=C), nu(37), nu(2), nu(11), and nu(38) bands), probably reflecting different distortions of heMe structure caused by the out-of-plane displaceMent of the heMe iron due to tyrosine coordination. Below 900 cM(-1), Hb M Iwate [alpha(F8)His --> Tyr] exhibited a distinct spectral pattern for nu(15), gaMMa(11), delta(C(beta)C(a)C(b))(2,4), and delta(C(beta)C(c)C(d))(6,7) coMpared to that of Hb M Boston [alpha(E7)His --> Tyr], although both heMe irons are coordinated by Tyr. The beta-abnorMal Hb M variants, naMely, Hb M Hyde Park [beta(F8)His --> Tyr], Hb M Saskatoon [beta(E7)His --> Tyr], and Hb M Milwaukee [beta(E11)Val --> Glu], displayed RR band patterns siMilar to that of MetHb A, but with soMe Minor individual differences. The RR bands characteristic of the Met-subunits of Hb M's totally disappeared by cheMical reduction, and the ferrous heMe of abnorMal subunits was no longer bonded with Tyr or Glu. They were bonded to the distal (E7) or proxiMal (F8) His, and this was confirMed by the presence of the nu(Fe-His) Mode at 215 cM(-1) in the 441.6-nM excited RR spectra. A possible involveMent of heMe distortion in differences of reducibility of abnorMal subunits and oxygen affinity of norMal subunits is discussed.

  • HeMe structure of HeMoglobin M Iwate [alpha 87(F8)His-->Tyr]: a UV and visible resonance RaMan study.
    Biochemistry, 2000
    Co-Authors: Masako Nagai, Y. Jin, Shigenori Nagatomo, Michihiko Aki, H Sakai, Teizo Kitagawa
    Abstract:

    HeMe structures of a natural Mutant HeMoglobin (Hb), Hb M Iwate [alpha87(F8)His-->Tyr], and protonation of its F8-Tyr were exaMined with the 244-nM excited UV resonance RaMan (UVRR) and the 406.7- and 441.6-nM excited visible resonance RaMan (RR) spectroscopy. It was clarified froM the UVRR bands at 1605 and 1166 cM(-)(1) characteristic of tyrosinate that the tyrosine (F8) of the abnorMal subunit in Hb M Iwate adopts a deprotonated forM. UV RaMan bands of other Tyr residues indicated that the protein takes the T-quaternary structure even in the Met forM. Although both heMes of alpha and beta subunits in MetHb A take a six-coordinate (6c) high-spin structure, the 406.7-nM excited RR spectruM of MetHb M Iwate indicated that the abnorMal alpha subunit adopts a 5c high-spin structure. The present results and our previous observation of the nu(Fe)(-)(O(tyrosine)) RaMan band [Nagai et al. (1989) BiocheMistry 28, 2418-2422] have proved that F8-tyrosinate is covalently bound to Fe(III) heMe in the alpha subunit of Hb M Iwate. As a result, peripheral groups of porphyrin ring, especially the vinyl and the propionate side chains, were so strongly influenced that the RR spectruM in the low-frequency region excited at 406.7 nM is distinctly changed froM the norMal pattern. When Hb M Iwate was fully reduced, the characteristic UVRR bands of tyrosinate disappeared and the RaMan bands of tyrosine at 1620 (Y8a), 1207 (Y7a), and 1177 cM(-)(1) (Y9a) increased in intensity. Coordination of distal His(E7) to the Fe(II) heMe in the reduced alpha subunit of Hb M Iwate was proved by the observation of the nu(Fe)(-)(His) RR band in the 441.6-nM excited RR spectruM at the saMe frequency as that of its isolated alpha chain. The effects of the distal-His coordination on the heMe appeared as a distortion of the peripheral groups of heMe. A possible MechanisM for the forMation of a Fe(III)-tyrosinate bond in Hb M Iwate is discussed.

Yukifumi Nagai - One of the best experts on this subject based on the ideXlab platform.

  • Differences in coordination states of substituted tyrosine residues and quaternary structures aMong HeMoglobin M probed by resonance RaMan spectroscopy
    JBIC Journal of Biological Inorganic Chemistry, 2010
    Co-Authors: Yayoi Aki, Kiyohiro Imai, Masako Nagai, Yukifumi Nagai, Shigenori Nagatomo, Michihiko Aki, Akira Sato, Minoru Kubo, Teizo Kitagawa
    Abstract:

    AMong the four types of HeMoglobin (Hb) M with a substitution of a tyrosine (Tyr) for either the proxiMal (F8) or distal (E7) histidine in the α or β subunits, only Hb M Saskatoon (βE7Tyr) assuMes a hexacoordinate structure and its abnorMal subunits can be reduced readily by MetHeMoglobin (MetHb) reductase. This is distinct froM the other three M Hbs. To gain new insight into the cause of the difference, we exaMined the ionization states of E7 and F8 Tyrs by UV resonance RaMan (RR) spectroscopy and Fe–O(Tyr) bonding by visible RR spectroscopy. Hb M Iwate (αF8Tyr), Hb M Boston (αE7Tyr), and Hb M Hyde Park (βF8Tyr) exhibited two extra UV RR bands at 1,603 cM^−1 (Y8a′) and 1,167 cM^−1 (Y9a′) arising froM deprotonated (ionized) Tyr, but Hb M Saskatoon displayed the UV RR bands of protonated (unionized) Tyr at 1,620 and 1,175 cM^−1 in addition to those of deprotonated Tyr. Evidence for the bonding of both ionization states of Tyr to the heMe in Hb M Saskatoon was provided by visible RR spectroscopy. These results indicate that βE7Tyr of Hb M Saskatoon is in equilibriuM between protonated and deprotonated forMs, which is responsible for facile reducibility. CoMparison of the UV RR spectral features of MetHb M with that of MetHb A has revealed that MetHb M Saskatoon and MetHb M Hyde Park are in the R (relaxed) structure, siMilar to that of MetHb A, whereas MetHb M Iwate, MetHb M Boston and MetHb M Milwaukee are in the T (tense) quaternary structure.

  • HeMe structures of five variants of HeMoglobin M probed by resonance RaMan spectroscopy.
    Biochemistry, 2004
    Co-Authors: Y. Jin, Masako Nagai, Yukifumi Nagai, Shigenori Nagatomo, Teizo Kitagawa
    Abstract:

    The alpha-abnorMal HeMoglobin (Hb) M variants show physiological properties different froM the beta-abnorMal Hb M variants, that is, extreMely low oxygen affinity of the norMal subunit and extraordinary resistance to both enzyMatic and cheMical reduction of the abnorMal Met-subunit. To get insight into the contribution of heMe structures to these differences aMong Hb M's, we exaMined the 406.7-nM excited resonance RaMan (RR) spectra of five Hb M's in the frequency region froM 1700 to 200 cM(-1). In the high-frequency region, profound differences between Met-alpha and Met-beta abnorMal subunits were observed for the in-plane skeletal Modes (the nu(C=C), nu(37), nu(2), nu(11), and nu(38) bands), probably reflecting different distortions of heMe structure caused by the out-of-plane displaceMent of the heMe iron due to tyrosine coordination. Below 900 cM(-1), Hb M Iwate [alpha(F8)His --> Tyr] exhibited a distinct spectral pattern for nu(15), gaMMa(11), delta(C(beta)C(a)C(b))(2,4), and delta(C(beta)C(c)C(d))(6,7) coMpared to that of Hb M Boston [alpha(E7)His --> Tyr], although both heMe irons are coordinated by Tyr. The beta-abnorMal Hb M variants, naMely, Hb M Hyde Park [beta(F8)His --> Tyr], Hb M Saskatoon [beta(E7)His --> Tyr], and Hb M Milwaukee [beta(E11)Val --> Glu], displayed RR band patterns siMilar to that of MetHb A, but with soMe Minor individual differences. The RR bands characteristic of the Met-subunits of Hb M's totally disappeared by cheMical reduction, and the ferrous heMe of abnorMal subunits was no longer bonded with Tyr or Glu. They were bonded to the distal (E7) or proxiMal (F8) His, and this was confirMed by the presence of the nu(Fe-His) Mode at 215 cM(-1) in the 441.6-nM excited RR spectra. A possible involveMent of heMe distortion in differences of reducibility of abnorMal subunits and oxygen affinity of norMal subunits is discussed.

Michihiko Aki - One of the best experts on this subject based on the ideXlab platform.

  • Differences in coordination states of substituted tyrosine residues and quaternary structures aMong HeMoglobin M probed by resonance RaMan spectroscopy
    JBIC Journal of Biological Inorganic Chemistry, 2010
    Co-Authors: Yayoi Aki, Kiyohiro Imai, Masako Nagai, Yukifumi Nagai, Shigenori Nagatomo, Michihiko Aki, Akira Sato, Minoru Kubo, Teizo Kitagawa
    Abstract:

    AMong the four types of HeMoglobin (Hb) M with a substitution of a tyrosine (Tyr) for either the proxiMal (F8) or distal (E7) histidine in the α or β subunits, only Hb M Saskatoon (βE7Tyr) assuMes a hexacoordinate structure and its abnorMal subunits can be reduced readily by MetHeMoglobin (MetHb) reductase. This is distinct froM the other three M Hbs. To gain new insight into the cause of the difference, we exaMined the ionization states of E7 and F8 Tyrs by UV resonance RaMan (RR) spectroscopy and Fe–O(Tyr) bonding by visible RR spectroscopy. Hb M Iwate (αF8Tyr), Hb M Boston (αE7Tyr), and Hb M Hyde Park (βF8Tyr) exhibited two extra UV RR bands at 1,603 cM^−1 (Y8a′) and 1,167 cM^−1 (Y9a′) arising froM deprotonated (ionized) Tyr, but Hb M Saskatoon displayed the UV RR bands of protonated (unionized) Tyr at 1,620 and 1,175 cM^−1 in addition to those of deprotonated Tyr. Evidence for the bonding of both ionization states of Tyr to the heMe in Hb M Saskatoon was provided by visible RR spectroscopy. These results indicate that βE7Tyr of Hb M Saskatoon is in equilibriuM between protonated and deprotonated forMs, which is responsible for facile reducibility. CoMparison of the UV RR spectral features of MetHb M with that of MetHb A has revealed that MetHb M Saskatoon and MetHb M Hyde Park are in the R (relaxed) structure, siMilar to that of MetHb A, whereas MetHb M Iwate, MetHb M Boston and MetHb M Milwaukee are in the T (tense) quaternary structure.

  • HeMe structure of HeMoglobin M Iwate [alpha 87(F8)His-->Tyr]: a UV and visible resonance RaMan study.
    Biochemistry, 2000
    Co-Authors: Masako Nagai, Y. Jin, Shigenori Nagatomo, Michihiko Aki, H Sakai, Teizo Kitagawa
    Abstract:

    HeMe structures of a natural Mutant HeMoglobin (Hb), Hb M Iwate [alpha87(F8)His-->Tyr], and protonation of its F8-Tyr were exaMined with the 244-nM excited UV resonance RaMan (UVRR) and the 406.7- and 441.6-nM excited visible resonance RaMan (RR) spectroscopy. It was clarified froM the UVRR bands at 1605 and 1166 cM(-)(1) characteristic of tyrosinate that the tyrosine (F8) of the abnorMal subunit in Hb M Iwate adopts a deprotonated forM. UV RaMan bands of other Tyr residues indicated that the protein takes the T-quaternary structure even in the Met forM. Although both heMes of alpha and beta subunits in MetHb A take a six-coordinate (6c) high-spin structure, the 406.7-nM excited RR spectruM of MetHb M Iwate indicated that the abnorMal alpha subunit adopts a 5c high-spin structure. The present results and our previous observation of the nu(Fe)(-)(O(tyrosine)) RaMan band [Nagai et al. (1989) BiocheMistry 28, 2418-2422] have proved that F8-tyrosinate is covalently bound to Fe(III) heMe in the alpha subunit of Hb M Iwate. As a result, peripheral groups of porphyrin ring, especially the vinyl and the propionate side chains, were so strongly influenced that the RR spectruM in the low-frequency region excited at 406.7 nM is distinctly changed froM the norMal pattern. When Hb M Iwate was fully reduced, the characteristic UVRR bands of tyrosinate disappeared and the RaMan bands of tyrosine at 1620 (Y8a), 1207 (Y7a), and 1177 cM(-)(1) (Y9a) increased in intensity. Coordination of distal His(E7) to the Fe(II) heMe in the reduced alpha subunit of Hb M Iwate was proved by the observation of the nu(Fe)(-)(His) RR band in the 441.6-nM excited RR spectruM at the saMe frequency as that of its isolated alpha chain. The effects of the distal-His coordination on the heMe appeared as a distortion of the peripheral groups of heMe. A possible MechanisM for the forMation of a Fe(III)-tyrosinate bond in Hb M Iwate is discussed.