The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Michael G. Rossmann - One of the best experts on this subject based on the ideXlab platform.
-
Courageous science: structural studies of bluetongue Virus Core
Structure (London England : 1993), 1999Co-Authors: Michael G. Rossmann, Yizhi TaoAbstract:The structure of the bluetongue Virus Core was recently reported and represents the largest structure determined to atomic resolution. As a biological machine capable of RNA transcription, the structure has immense biological significance.
-
structure of semliki forest Virus Core protein
Proteins, 1997Co-Authors: Hok-kin Choi, Gerd Wengler, Sukyeong Lee, Michael G. RossmannAbstract:AlphaViruses are enveloped, insect-borne Viruses, which contain a positive-sense RNA genome. The protein capsid is surrounded by a lipid membrane, which is penetrated by glycoprotein spikes. The structure of the Sindbis Virus (SINV) (the type Virus) Core protein (SCP) was previously determined and found to have a chymotrypsin-like structure. SCP is a serine proteinase which cleaves itself from a polyprotein. Semliki Forest Virus (SFV) is among the most distantly related alphaViruses to SINV. Similar to SCP, autocatalysis is inhibited in SFCP after cleavage of the polyprotein by leaving the carboxy-terminal tryptophan in the specificity pocket. The structures of two different crystal forms (I and II) of SFV Core protein (SFCP) have been determined to 3.0 A and 3.3 A resolution, respectively. The SFCP monomer backbone structure is very similar to that of SCP. The dimeric association between monomers, A and B, found in two different crystal forms of SCP is also present in both crystal forms of SFCP. However, a third monomer, C, occurs in SFCP crystal form I. While monomers A and B make a tail-to-tail dimer contact, monomers B and C make a head-to-head dimer contact. A hydrophobic pocket on the surface of the capsid protein, the proposed site of binding of the E2 glycoprotein, has large conformational differences with respect to SCP and, in contrast to SCP, is found devoid of bound peptide. In particular, Tyr184 is pointing out of the hydrophobic pocket in SFCP, whereas the equivalent tyrosine in SCP is pointing into the pocket. The conformation of Tyr184, found in SFCP, is consistent with its availability for iodination, as observed in the homologous SINV Cores. This suggests, by comparison with SCP, that E2 binding to Cores causes major conformational changes, including the burial of Tyr184, which would stabilize the intact Virus on budding from an infected cell. The head-to-tail contacts found in the pentameric and hexameric associations within the virion utilize the same monomer surface regions as found in the crystalline dimer interfaces. Proteins 27:345–359, 1997. © 1997 Wiley-Liss, Inc.
-
Refined Structure of Sindbis Virus Core Protein and Comparison with Other Chymotrypsin-like Serine Proteinase Structures
Journal of molecular biology, 1993Co-Authors: Liang Tong, Gerd Wengler, Michael G. RossmannAbstract:Abstract Crystal forms 2 and 3 of Sindbis Virus Core protein have been refined to 2·8 A and 3·0 A resolution, respectively. The three independent molecular copies in the two crystal forms are essentially identical, except for regions where the molecules are involved in different crystal packing interactions. The overall polypeptide backbone fold of Sindbis Virus Core protein is similar to other chymotrypsin-like serine proteinase structures despite a lack of significant sequence homology. Detailed analysis revealed differences in the catalytic triad and the substrate binding pockets between the Sindbis Virus Core protein and the other serine proteinases. The catalytic aspartic acid residue (Asp 163 ) and residue Asp 214 (corresponding to Asp194 in chymotrypsin) are partially exposed to solvent in Sindbis Virus Core protein. Chymotrypsin Ser214, hydrogen bonded to the catalytic aspartic acid residue in all other serine proteinase structures, is changed to Leu 231 in Sindbis Virus Core protein. Deletions in the loop regions on the surface of the protein account for the smaller size of the ordered part of Sindbis Virus Core protein (151 residues) as compared to chymotrypsin (236 residues), and permits the cis autocatalytic cleavage of the polyprotein to produce the viral capsid protein.
-
The structure determination of Sindbis Virus Core protein using isomorphous replacement and molecular replacement averaging between two crystal forms.
Acta Crystallographica Section A Foundations of Crystallography, 1992Co-Authors: Liang Tong, Hok-kin Choi, Wladek Minor, Michael G. RossmannAbstract:The structure of Sindbis Virus Core protein has been determined by a combination of multiple isomorphous replacement and molecular replacement averaging techniques. The multiple isomorphous replacement phase determinations were made for two crystal forms (P21 and P432~2 ) of the Core protein. The real-space molecular replacement averaging was subsequently carded out between two copies of the protein per asymmetric unit in the monoclinic form and one copy in the tetragonal form. This greatly improved the quality of the electron density maps. The Sindbis Virus Core protein polypeptide could be
-
The structure determination of Sindbis Virus Core protein using isomorphous replacement and molecular replacement averaging between two crystal forms.
Acta crystallographica. Section A Foundations of crystallography, 1992Co-Authors: Liang Tong, Hok-kin Choi, Wladek Minor, Michael G. RossmannAbstract:The structure of Sindbis Virus Core protein has been determined by a combination of multiple isomorphous replacement and molecular replacement averaging techniques. The multiple isomorphous replacement phase determinations were made for two crystal forms (P2(1) and P4(3)2(1)2) of the Core protein. The real-space molecular replacement averaging was subsequently carried out between two copies of the protein per asymmetric unit in the monoclinic form and one copy in the tetragonal form. This greatly improved the quality of the electron density maps. The Sindbis Virus Core protein polypeptide could be traced and related to the known amino acid sequence. The averaging procedure between different crystal forms, as described in this paper, should be generally applicable to other systems.
Liang Tong - One of the best experts on this subject based on the ideXlab platform.
-
Refined Structure of Sindbis Virus Core Protein and Comparison with Other Chymotrypsin-like Serine Proteinase Structures
Journal of molecular biology, 1993Co-Authors: Liang Tong, Gerd Wengler, Michael G. RossmannAbstract:Abstract Crystal forms 2 and 3 of Sindbis Virus Core protein have been refined to 2·8 A and 3·0 A resolution, respectively. The three independent molecular copies in the two crystal forms are essentially identical, except for regions where the molecules are involved in different crystal packing interactions. The overall polypeptide backbone fold of Sindbis Virus Core protein is similar to other chymotrypsin-like serine proteinase structures despite a lack of significant sequence homology. Detailed analysis revealed differences in the catalytic triad and the substrate binding pockets between the Sindbis Virus Core protein and the other serine proteinases. The catalytic aspartic acid residue (Asp 163 ) and residue Asp 214 (corresponding to Asp194 in chymotrypsin) are partially exposed to solvent in Sindbis Virus Core protein. Chymotrypsin Ser214, hydrogen bonded to the catalytic aspartic acid residue in all other serine proteinase structures, is changed to Leu 231 in Sindbis Virus Core protein. Deletions in the loop regions on the surface of the protein account for the smaller size of the ordered part of Sindbis Virus Core protein (151 residues) as compared to chymotrypsin (236 residues), and permits the cis autocatalytic cleavage of the polyprotein to produce the viral capsid protein.
-
The structure determination of Sindbis Virus Core protein using isomorphous replacement and molecular replacement averaging between two crystal forms.
Acta Crystallographica Section A Foundations of Crystallography, 1992Co-Authors: Liang Tong, Hok-kin Choi, Wladek Minor, Michael G. RossmannAbstract:The structure of Sindbis Virus Core protein has been determined by a combination of multiple isomorphous replacement and molecular replacement averaging techniques. The multiple isomorphous replacement phase determinations were made for two crystal forms (P21 and P432~2 ) of the Core protein. The real-space molecular replacement averaging was subsequently carded out between two copies of the protein per asymmetric unit in the monoclinic form and one copy in the tetragonal form. This greatly improved the quality of the electron density maps. The Sindbis Virus Core protein polypeptide could be
-
The structure determination of Sindbis Virus Core protein using isomorphous replacement and molecular replacement averaging between two crystal forms.
Acta crystallographica. Section A Foundations of crystallography, 1992Co-Authors: Liang Tong, Hok-kin Choi, Wladek Minor, Michael G. RossmannAbstract:The structure of Sindbis Virus Core protein has been determined by a combination of multiple isomorphous replacement and molecular replacement averaging techniques. The multiple isomorphous replacement phase determinations were made for two crystal forms (P2(1) and P4(3)2(1)2) of the Core protein. The real-space molecular replacement averaging was subsequently carried out between two copies of the protein per asymmetric unit in the monoclinic form and one copy in the tetragonal form. This greatly improved the quality of the electron density maps. The Sindbis Virus Core protein polypeptide could be traced and related to the known amino acid sequence. The averaging procedure between different crystal forms, as described in this paper, should be generally applicable to other systems.
Jm Diprose - One of the best experts on this subject based on the ideXlab platform.
-
The bluetongue Virus Core: a nano-scale transcription machine.
Virus research, 2004Co-Authors: Peter P C Mertens, Jm DiproseAbstract:The replication phase of the bluetongue Virus (BTV) infection cycle is initiated when the Virus Core is delivered into the cytoplasm of a susceptible host cell. The 10 segments of the viral genome remain packaged within the Core throughout the replication cycle, helping to prevent the activation of host defence mechanisms that would be caused by direct contact between the dsRNA and the host cell cytoplasm. However, the BTV Core is a biochemically active 'nano-scale' machine, which can simultaneously and repeatedly transcribe mRNA from each of the 10 genome segments, which are packaged as a liquid crystal array within a central cavity. These mRNAs, which are also capped and methylated within the Core, are extruded into the cytoplasm through pores at the vertices of the icosahedral structure, where they are translated into viral proteins. One copy of each of the viral mRNAs is also assembled with these newly synthesised proteins to form nascent Virus particles, which mature by a process that involves -ve RNA strand synthesis on the +ve stand template, thereby reforming dsRNA genome segments within progeny Virus Cores. The structure of the BTV Core particle has been determined to atomic resolution by X-ray crystallography, revealing the organisation and interactions of its major protein components (VP3(T2)-subCore shell and VP7(T13) outer Core layer) and important features of the packaged dsRNA. By soaking crystals of BTV Cores with metal ions and substrates/products of the transcription reactions prior to analysis by X-ray crystallography, then constructing difference maps, it has been possible to identify binding sites and entry/exit routes for these ions, substrates and products. This has revealed how BTV solves the many logistical problems of multiple and simultaneous transcription from the 10 genome segments within the confined space of the Core particle. The crystal structure of the BTV Core has also revealed an outer surface festooned with dsRNA. This may represent a further protective strategy adopted by the Virus to prevent host cell shut-off, by sequestering any dsRNA that may be released from damaged particles.
-
translocation portals for the substrates and products of a viral transcription complex the bluetongue Virus Core
The EMBO Journal, 2001Co-Authors: Jm Diprose, Jn Burroughs, A. Goldsmith, P. Gouet, R. Malby, S. Zientara, Geoff Sutton, Ian M Overton, Peter P C MertensAbstract:The bluetongue Virus Core is a molecular machine that simultaneously and repeatedly transcribes mRNA from 10 segments of viral double-stranded RNA, packaged in a liquid crystalline array. To determine how the logistical problems of transcription within a sealed shell are solved, Core crystals were soaked with various ligands and analysed by X-ray crystallography. Mg2+ ions produce a slight expansion of the capsid around the 5-fold axes. Oligonucleotide soaks demonstrate that the 5-fold pore, opened up by this expansion, is the exit site for mRNA, whilst nucleotide soaks pinpoint a separate binding site that appears to be a selective channel for the entry and exit of substrates and by-products. Finally, nucleotides also bind to the outer Core layer, providing a substrate sink.
-
Translocation portals for the substrates and products of a viral transcription complex: the bluetongue Virus Core.
EMBO Journal, 2001Co-Authors: Jm Diprose, Jn Burroughs, Gc Sutton, A. Goldsmith, P. Gouet, R. Malby, I. Overton, S. Zientara, Pp Mertens, Di StuartAbstract:The bluetongue Virus Core is a molecular machine that simultaneously and repeatedly transcribes mRNA from 10 segments of viral double-stranded RNA, packaged in a liquid crystalline array. To determine how the logistical problems of transcription within a sealed shell are solved, Core crystals were soaked with various ligands and analysed by X-ray crystallography. Mg(2+) ions produce a slight expansion of the capsid around the 5-fold axes. Oligonucleotide soaks demonstrate that the 5-fold pore, opened up by this expansion, is the exit site for mRNA, whilst nucleotide soaks pinpoint a separate binding site that appears to be a selective channel for the entry and exit of substrates and by-products. Finally, nucleotides also bind to the outer Core layer, providing a substrate sink.The bluetongue Virus Core is a molecular machine that simultaneously and repeatedly transcribes mRNA from 10 segments of viral double-stranded RNA, packaged in a liquid crystalline array. To determine how the logistical problems of transcription within a sealed shell are solved, Core crystals were soaked with various ligands and analysed by X-ray crystallography. Mg(2+) ions produce a slight expansion of the capsid around the 5-fold axes. Oligonucleotide soaks demonstrate that the 5-fold pore, opened up by this expansion, is the exit site for mRNA, whilst nucleotide soaks pinpoint a separate binding site that appears to be a selective channel for the entry and exit of substrates and by-products. Finally, nucleotides also bind to the outer Core layer, providing a substrate sink.
Peter P C Mertens - One of the best experts on this subject based on the ideXlab platform.
-
The bluetongue Virus Core: a nano-scale transcription machine.
Virus research, 2004Co-Authors: Peter P C Mertens, Jm DiproseAbstract:The replication phase of the bluetongue Virus (BTV) infection cycle is initiated when the Virus Core is delivered into the cytoplasm of a susceptible host cell. The 10 segments of the viral genome remain packaged within the Core throughout the replication cycle, helping to prevent the activation of host defence mechanisms that would be caused by direct contact between the dsRNA and the host cell cytoplasm. However, the BTV Core is a biochemically active 'nano-scale' machine, which can simultaneously and repeatedly transcribe mRNA from each of the 10 genome segments, which are packaged as a liquid crystal array within a central cavity. These mRNAs, which are also capped and methylated within the Core, are extruded into the cytoplasm through pores at the vertices of the icosahedral structure, where they are translated into viral proteins. One copy of each of the viral mRNAs is also assembled with these newly synthesised proteins to form nascent Virus particles, which mature by a process that involves -ve RNA strand synthesis on the +ve stand template, thereby reforming dsRNA genome segments within progeny Virus Cores. The structure of the BTV Core particle has been determined to atomic resolution by X-ray crystallography, revealing the organisation and interactions of its major protein components (VP3(T2)-subCore shell and VP7(T13) outer Core layer) and important features of the packaged dsRNA. By soaking crystals of BTV Cores with metal ions and substrates/products of the transcription reactions prior to analysis by X-ray crystallography, then constructing difference maps, it has been possible to identify binding sites and entry/exit routes for these ions, substrates and products. This has revealed how BTV solves the many logistical problems of multiple and simultaneous transcription from the 10 genome segments within the confined space of the Core particle. The crystal structure of the BTV Core has also revealed an outer surface festooned with dsRNA. This may represent a further protective strategy adopted by the Virus to prevent host cell shut-off, by sequestering any dsRNA that may be released from damaged particles.
-
translocation portals for the substrates and products of a viral transcription complex the bluetongue Virus Core
The EMBO Journal, 2001Co-Authors: Jm Diprose, Jn Burroughs, A. Goldsmith, P. Gouet, R. Malby, S. Zientara, Geoff Sutton, Ian M Overton, Peter P C MertensAbstract:The bluetongue Virus Core is a molecular machine that simultaneously and repeatedly transcribes mRNA from 10 segments of viral double-stranded RNA, packaged in a liquid crystalline array. To determine how the logistical problems of transcription within a sealed shell are solved, Core crystals were soaked with various ligands and analysed by X-ray crystallography. Mg2+ ions produce a slight expansion of the capsid around the 5-fold axes. Oligonucleotide soaks demonstrate that the 5-fold pore, opened up by this expansion, is the exit site for mRNA, whilst nucleotide soaks pinpoint a separate binding site that appears to be a selective channel for the entry and exit of substrates and by-products. Finally, nucleotides also bind to the outer Core layer, providing a substrate sink.
S J Keller - One of the best experts on this subject based on the ideXlab platform.
-
Phosphorylation of vaccinia Virus Core proteins during transcription in vitro.
Journal of virology, 1991Co-Authors: N Moussatche, S J KellerAbstract:The phosphorylation of vaccinia Virus Core proteins has been studied in vitro during viral transcription. The incorporation of [gamma-32P]ATP into protein is linear for the first 2 min of the reaction, whereas incorporation of [3H]UTP into RNA lags for 1 to 2 min before linear synthesis. At least 12 different proteins are phosphorylated on autoradiograms of acrylamide gels, and the majority of label is associated with low-molecular-weight proteins. If the transcription reaction is reduced by dropping the pH to 7 from its optimal of 8.5, two proteins (70 and 80 kDa) are no longer phosphorylated. RNA isolated from the pH 7 transcription reaction hybridized primarily to the vaccinia Virus HindIII DNA fragments D to F, whereas the transcripts synthesized at pH 8.5 hybridized to almost all of the HindIII-digested vaccinia Virus DNA fragments. The differences between the pH 7.0 and 8.5 transcription reactions in phosphorylation and transcription could be eliminated by preincubating the viral Cores with 2 mM ATP. In sum, the results suggest that the phosphorylation of the 70- and 80-kDa peptides may contribute to the regulation of early transcription.
