The Experts below are selected from a list of 174 Experts worldwide ranked by ideXlab platform
Patrick Robberecht - One of the best experts on this subject based on the ideXlab platform.
-
Molecular cloning and functional characterization of a human VIP receptor from SUP-T1 lymphoblasts.
Biochemical and biophysical research communications, 1994Co-Authors: Michal Svoboda, Magali Waelbroeck, Michèle Tastenoy, J. Vanrampelbergh, J.f. Goossens, P. Deneef, Patrick RobberechtAbstract:Abstract We have cloned and sequenced a cDNA isolated from a human SUP-T1 lymphoblast cell line library. It encoded a 457 amino acids protein having 87% identity with the rat PACAP type II, VIP2 receptor. Chinese hamster ovary (CHO) cells stably transfected with cloned cDNA expressed a specific binding of 125I[Acetyl-His1]PACAP-27. This binding was inhibited by GTP, and by the peptides Helodermin, VIP, PACAP-27 and PACAP-38 that also stimulated adenylate cyclase activity. The order of potency was PACAP-38 > VIP ≥ Helodermin ≥ PACAP-27. Comparison of the results in two cell lines expressing different receptor densities suggested that Helodermin and PACAP-38 had a higher intrinsic activity than VIP and PACAP-27.
-
From lizard Helodermin to mammalian Helodermin- and pacap-preferring VIP receptors
Biomedical Research-tokyo, 1993Co-Authors: Jean Christophe, André Vandermeers, Marie-claire Vandermeers-piret, Patrick RobberechtAbstract:Calcyclin, one of Ca 2+ binding proteins, was originally identified as the product of the 2A9 gene, the mRNA of which is increased by the stimulation of serum, PDGF, and EGF in quiescent fibroblast. Recently, we found calcyclin associated protein, CAP-SO. The biochemical and structural analysis of CAP-SO revealed that CAP-SO is a member of annexin family, which binds to calcium and phospholipid. CAP-SO specifically binds to calcyclin, and is located in nuclei of fibroblast. These findings suggest that calcyclin-CAP-SO may be involved in the regulation of cell proliferation
-
Helodermin-like immunoreactivity is artefactually increased in bovine brain by the presence of calmodulin
Biomedical Research-tokyo, 1992Co-Authors: André Vandermeers, Patrick Robberecht, Marie-claire Vandermeers-piret, Yassir Bounjoua, Jean ChristopheAbstract:A chromatographic procedure was developed to purify to homogeneity the Helodermin-immunoreactive material present in bovine brain. Most of that material turned out to be calmodulin. Our results suggest that at a least a large part of the Helodermin-like material claimed to be present in mammalian tissues is an artefact due to the high affinity binding of [ 125 I]-Helodermin to calmodulin
-
The activation of adenylate cyclase by pituitary adenylate cyclase activating polypeptide (PACAP) via Helodermin-preferring VIP receptors in human SUP-T1 lymphoblastic membranes
Biochimica et biophysica acta, 1991Co-Authors: Philippe Gourlet, André Vandermeers, Philippe De Neef, Patrick Robberecht, Marie-claire Vandermeers-piret, M.c. Woussen-colle, Jean ChristopheAbstract:Abstract Competition binding curves, using [ 125 I-acetyl-His 1 ]PACAP-27 as radioligand and dose-effect curves of adenylate cyclase activation in human SUP-T1 lymphoblastic membranes showed that PACAP-27 and PACAP-38 stimulate the enzyme through a single class of Helodermin-preferring VIP receptors with the following order of potency: Helodermin= [acetyl-His 1 ]PACAP-27 >PACAP-38 >PACAP-27 >VIP. PACAP (6–27) ( K i 0.5-0.8 μM) and and [Des-His 1 , Asn 3 ]PACAP-27 ( K i 1–2 μM) acted as competitive antagonists. Using a series of 13 PACAP-27 analogues and fragments and three VIP analogues, we identified positions 1, 2, 3, 9 and 13 in PACAP-27 as being of importance for high-affinity binding. Thus, we added further evidence for considering that the present Helodermin-preferring VIP receptors, when compared to a majority of VIP receptors and PACAP receptors, exhibit an original specificity pattern.
-
Molecular characterization of Helodermin-preferring VIP receptors in SUP T1 lymphoma cells: evidence for receptor glycosylation.
Journal of receptor research, 1991Co-Authors: Philippe Gourlet, Patrick Robberecht, Jean ChristopheAbstract:AbstractCross-linking of [125I]Helodermin to human SUP-T1 lymphoblasts with bis[2-(succinimidooxycarbonyloxy)ethyl]sulfone (BSOCOES) revealed a 63 K binding protein. This cross-linking was inhibited by Helodermin and VIP. In cells submitted for 3–4 days to 0.2 μg/ml tunicamycin, the Mr of an increasing proportion of Helodermin-preferring receptors was reduced to 50 K and the total number of receptors was decreased by about 50%, without alteration in binding affinity and specificity. In parallel, the VIP-mediated adenylate cyclase stimulation was reduced by 30% with no change in NaF-, Gpp[NH]p-, and PGE1-stimulations. We conclude that a proper N-glycosylation of Helodermin-preferring VIP receptors is required for normal receptor targeting and turnover but not for ligand binding and adenylate cyclase coupling.
Jean Christophe - One of the best experts on this subject based on the ideXlab platform.
-
From lizard Helodermin to mammalian Helodermin- and pacap-preferring VIP receptors
Biomedical Research-tokyo, 1993Co-Authors: Jean Christophe, André Vandermeers, Marie-claire Vandermeers-piret, Patrick RobberechtAbstract:Calcyclin, one of Ca 2+ binding proteins, was originally identified as the product of the 2A9 gene, the mRNA of which is increased by the stimulation of serum, PDGF, and EGF in quiescent fibroblast. Recently, we found calcyclin associated protein, CAP-SO. The biochemical and structural analysis of CAP-SO revealed that CAP-SO is a member of annexin family, which binds to calcium and phospholipid. CAP-SO specifically binds to calcyclin, and is located in nuclei of fibroblast. These findings suggest that calcyclin-CAP-SO may be involved in the regulation of cell proliferation
-
Helodermin-like immunoreactivity is artefactually increased in bovine brain by the presence of calmodulin
Biomedical Research-tokyo, 1992Co-Authors: André Vandermeers, Patrick Robberecht, Marie-claire Vandermeers-piret, Yassir Bounjoua, Jean ChristopheAbstract:A chromatographic procedure was developed to purify to homogeneity the Helodermin-immunoreactive material present in bovine brain. Most of that material turned out to be calmodulin. Our results suggest that at a least a large part of the Helodermin-like material claimed to be present in mammalian tissues is an artefact due to the high affinity binding of [ 125 I]-Helodermin to calmodulin
-
The activation of adenylate cyclase by pituitary adenylate cyclase activating polypeptide (PACAP) via Helodermin-preferring VIP receptors in human SUP-T1 lymphoblastic membranes
Biochimica et biophysica acta, 1991Co-Authors: Philippe Gourlet, André Vandermeers, Philippe De Neef, Patrick Robberecht, Marie-claire Vandermeers-piret, M.c. Woussen-colle, Jean ChristopheAbstract:Abstract Competition binding curves, using [ 125 I-acetyl-His 1 ]PACAP-27 as radioligand and dose-effect curves of adenylate cyclase activation in human SUP-T1 lymphoblastic membranes showed that PACAP-27 and PACAP-38 stimulate the enzyme through a single class of Helodermin-preferring VIP receptors with the following order of potency: Helodermin= [acetyl-His 1 ]PACAP-27 >PACAP-38 >PACAP-27 >VIP. PACAP (6–27) ( K i 0.5-0.8 μM) and and [Des-His 1 , Asn 3 ]PACAP-27 ( K i 1–2 μM) acted as competitive antagonists. Using a series of 13 PACAP-27 analogues and fragments and three VIP analogues, we identified positions 1, 2, 3, 9 and 13 in PACAP-27 as being of importance for high-affinity binding. Thus, we added further evidence for considering that the present Helodermin-preferring VIP receptors, when compared to a majority of VIP receptors and PACAP receptors, exhibit an original specificity pattern.
-
Molecular characterization of Helodermin-preferring VIP receptors in SUP T1 lymphoma cells: evidence for receptor glycosylation.
Journal of receptor research, 1991Co-Authors: Philippe Gourlet, Patrick Robberecht, Jean ChristopheAbstract:AbstractCross-linking of [125I]Helodermin to human SUP-T1 lymphoblasts with bis[2-(succinimidooxycarbonyloxy)ethyl]sulfone (BSOCOES) revealed a 63 K binding protein. This cross-linking was inhibited by Helodermin and VIP. In cells submitted for 3–4 days to 0.2 μg/ml tunicamycin, the Mr of an increasing proportion of Helodermin-preferring receptors was reduced to 50 K and the total number of receptors was decreased by about 50%, without alteration in binding affinity and specificity. In parallel, the VIP-mediated adenylate cyclase stimulation was reduced by 30% with no change in NaF-, Gpp[NH]p-, and PGE1-stimulations. We conclude that a proper N-glycosylation of Helodermin-preferring VIP receptors is required for normal receptor targeting and turnover but not for ligand binding and adenylate cyclase coupling.
-
PACAP VIP receptor in rat liver membranes
1991Co-Authors: Patrick Robberecht, Philippe De Neef, Akira Arimura, Philippe Gourlet, Annick Cauvin, Jean Christophe, Louis Buscail, Annick CauAbstract:23): G97-G102, 1991.-Pituitary adenylate cyclase activating peptide (PACAP) tested as PACAP-(l-38)NH, and PACAP-( l-27)NH2 and vasoactive intestinal polypeptide (VIP) were compared for their capacity to discriminate between high- and low-affinity VIP-preferring receptors that coexist in rat liver plasma membranes. This capacity was evaluated by the ability to 1) inhibit ‘251-labeled-PACAP- ( l-27)NH,, 1251-labeled-VIP, and 12”I-labeled-Helodermin binding and 2) to activate adenyl-ate cylase. PACAP- ( l-27)NH2 bound specifically and revers-ibly to three classes of binding sites, as revealed by analysis of binding curves. On high-affinity VIP receptors (tested specifi-cally by [ 12’1]- Helodermin binding), PACAP- ( l-38)NH2 showed lower affinity than PACAP- ( l-27)NH2 and VIP itself. On low-affinity VIP receptors, PACAP-(I-27)NH2 and-(l-38)NH2 showed similar modest affinity that was slightly highe
Philippe Gourlet - One of the best experts on this subject based on the ideXlab platform.
-
Analogues of VIP, Helodermin, and PACAP Discriminate between Rat and Human VIP1 and VIP2 Receptorsa
Annals of the New York Academy of Sciences, 1998Co-Authors: Philippe Gourlet, Magali Waelbroeck, André Vandermeers, Philippe De Neef, Jean Van Rampelbergh, Johnny Cnudde, Patrock RobberechtAbstract:Vasoactive intestinal polypeptide (VIP) acts through interaction with two subclasses of seven transmembrane G protein-coupled receptors named VIP1 and VIP2 receptors. These receptors have been cloned in different species, such as rat and human. Considering the different distribution of both receptor subclasses, there is considerable interest in the development of selective agonists and antagonists. The present study compares the binding properties of VIP, PACAP, GRF, secretin, and Helodermin analogues on recombinant rat and human VIP1 and VIP2 receptors. On both rat and human receptors, secretin and GRF had a higher affinity for the VIP1 receptor subtypes. The amino-shortened VIP, and the carboxy terminal-shortened VIP and PACAP analogues also presented a higher affinity for the VIP1 receptor. PHI, PHV, Helodermin, and helospectin were selective for the human VIP2 receptor subtypes. These results suggest that the helical structure of the carboxy terminal end is necessary for VIP2 recognition. The differences between species were the following: PHI, PHV, Helodermin, and helospectin had a higher affinity for the rat VIP1 receptor than for the human VIP1 receptor. On both rat and human receptors, D-Ala4 VIP and D-Phe4 VIP had a high affinity for the VIP1 receptor and a low affinity for the VIP2 receptor. Thus, three domains of the ligand involved in VIP1/VIP2 receptor discrimination were identified: the amino acid residue in position 4 ([D-Ala4], [D-Phe4]VIP), in positions 8 and 9 (the effects of Helodermin and helospectin), and the carboxy terminal end (the effects of the shortened VIP and pituitary adenylate cyclase activating polypeptide analogues).
-
The activation of adenylate cyclase by pituitary adenylate cyclase activating polypeptide (PACAP) via Helodermin-preferring VIP receptors in human SUP-T1 lymphoblastic membranes
Biochimica et biophysica acta, 1991Co-Authors: Philippe Gourlet, André Vandermeers, Philippe De Neef, Patrick Robberecht, Marie-claire Vandermeers-piret, M.c. Woussen-colle, Jean ChristopheAbstract:Abstract Competition binding curves, using [ 125 I-acetyl-His 1 ]PACAP-27 as radioligand and dose-effect curves of adenylate cyclase activation in human SUP-T1 lymphoblastic membranes showed that PACAP-27 and PACAP-38 stimulate the enzyme through a single class of Helodermin-preferring VIP receptors with the following order of potency: Helodermin= [acetyl-His 1 ]PACAP-27 >PACAP-38 >PACAP-27 >VIP. PACAP (6–27) ( K i 0.5-0.8 μM) and and [Des-His 1 , Asn 3 ]PACAP-27 ( K i 1–2 μM) acted as competitive antagonists. Using a series of 13 PACAP-27 analogues and fragments and three VIP analogues, we identified positions 1, 2, 3, 9 and 13 in PACAP-27 as being of importance for high-affinity binding. Thus, we added further evidence for considering that the present Helodermin-preferring VIP receptors, when compared to a majority of VIP receptors and PACAP receptors, exhibit an original specificity pattern.
-
Molecular characterization of Helodermin-preferring VIP receptors in SUP T1 lymphoma cells: evidence for receptor glycosylation.
Journal of receptor research, 1991Co-Authors: Philippe Gourlet, Patrick Robberecht, Jean ChristopheAbstract:AbstractCross-linking of [125I]Helodermin to human SUP-T1 lymphoblasts with bis[2-(succinimidooxycarbonyloxy)ethyl]sulfone (BSOCOES) revealed a 63 K binding protein. This cross-linking was inhibited by Helodermin and VIP. In cells submitted for 3–4 days to 0.2 μg/ml tunicamycin, the Mr of an increasing proportion of Helodermin-preferring receptors was reduced to 50 K and the total number of receptors was decreased by about 50%, without alteration in binding affinity and specificity. In parallel, the VIP-mediated adenylate cyclase stimulation was reduced by 30% with no change in NaF-, Gpp[NH]p-, and PGE1-stimulations. We conclude that a proper N-glycosylation of Helodermin-preferring VIP receptors is required for normal receptor targeting and turnover but not for ligand binding and adenylate cyclase coupling.
-
molecular characterization of Helodermin preferring evidence for receptor glycosylation vip receptors in sup ti lymphoma cells
1991Co-Authors: Philippe Gourlet, Patrock Robberecht, J ChristopheAbstract:TRACT Cross-linking of [ #‘I ] Helodermin to human SUP-TI lymphoblasts with bis[2-(succinimidooxycarbonyloxy)ethyl]sulfone (BSOCOES) revealed a 63 K binding protein. This cross-linking was inhibited by Helodermin and VIP. In cells subitted for 3-4 days to 0.2 pg/ml tunicamycin, the Mr of an increasing proprtion of helcdemin-pref erring receptors was reduced to 50 K and the total number of receptors was decreased by about 50 %, without alteration in binding affinity and specificity. In parallel, the VIP-mediated adenylate cyclase stimlation was reduced by 30 % with no change in NaF-, Gpp[NH]p-, and PGE -stimulations. We conclude that a proper N-glycosylation 04 Helodermin-preferring VIP receptors is required for normal receptor targeting and turnover but not for ligand binding and adenylate cyclase coupling.
-
PACAP VIP receptor in rat liver membranes
1991Co-Authors: Patrick Robberecht, Philippe De Neef, Akira Arimura, Philippe Gourlet, Annick Cauvin, Jean Christophe, Louis Buscail, Annick CauAbstract:23): G97-G102, 1991.-Pituitary adenylate cyclase activating peptide (PACAP) tested as PACAP-(l-38)NH, and PACAP-( l-27)NH2 and vasoactive intestinal polypeptide (VIP) were compared for their capacity to discriminate between high- and low-affinity VIP-preferring receptors that coexist in rat liver plasma membranes. This capacity was evaluated by the ability to 1) inhibit ‘251-labeled-PACAP- ( l-27)NH,, 1251-labeled-VIP, and 12”I-labeled-Helodermin binding and 2) to activate adenyl-ate cylase. PACAP- ( l-27)NH2 bound specifically and revers-ibly to three classes of binding sites, as revealed by analysis of binding curves. On high-affinity VIP receptors (tested specifi-cally by [ 12’1]- Helodermin binding), PACAP- ( l-38)NH2 showed lower affinity than PACAP- ( l-27)NH2 and VIP itself. On low-affinity VIP receptors, PACAP-(I-27)NH2 and-(l-38)NH2 showed similar modest affinity that was slightly highe
Stephen A. Wank - One of the best experts on this subject based on the ideXlab platform.
-
MOLECULAR CLONING OF THE Helodermin AND EXENDIN-4 CDNAS IN THE LIZARD : RELATIONSHIP TO VASOACTIVE INTESTINAL POLYPEPTIDE/PITUITARY ADENYLATE CYCLASE ACTIVATING POLYPEPTIDE AND GLUCAGON-LIKE PEPTIDE 1 AND EVIDENCE AGAINST THE EXISTENCE OF MAMMALIAN H
Journal of Biological Chemistry, 1998Co-Authors: Markus Pohl, Stephen A. WankAbstract:Abstract Helodermin and exendin-4, two peptides isolated from the salivary gland of the Gila monster,Heloderma suspectum, are approximately 50% homologous to vasoactive intestinal peptide (VIP) and glucagon-like peptide-1 (GLP-1), respectively, and interact with the mammalian receptors for VIP and GLP-1 with equal or higher affinity and efficacy. Immunohistochemical studies suggested the presence of Helodermin-like peptides in mammals. To determine whether Helodermin and exendin-4 are present in mammals and their evolutionary relationship to VIP and GLP-1, their cDNAs were first cloned from Gila monster salivary gland. Northern blots and reverse transcription-polymerase chain reaction of multiple Gila monster tissues identified ∼500-base pair transcripts only from salivary gland. Both Helodermin and exendin-4 full-length cDNAs were ∼500 base pairs long, and they encoded precursor proteins containing the entire amino acid sequence of Helodermin and exendin-4, as well as a 44- or 45-amino acid N-terminal extension peptide, respectively, having ∼60% homology. The size and structural organization of these cDNAs indicated that they were closely related to one another but markedly different from known cDNAs for the VIP/GLP-1 peptide family previously identified in both lower and higher evolved species. Cloning of the Gila monster VIP/peptide histidine isoleucine, pituitary adenylate cyclase activating polypeptide, and glucagon/GLP-1 cDNAs and Southern blotting of Gila monster DNA demonstrate the coexistence of separate genes for these peptides and suggests, along with the restricted salivary gland expression, that Helodermin and exendin-4 coevolved to serve a separate specialized function. Probing of a variety of rat and human tissues on Northern blots, human and rat Southern blots, and genomic and cDNA libraries with either Helodermin- or exendin-4-specific cDNAs failed to identify evidence for mammalian homologues. These data indicate that Helodermin and exendin-4 are not the precursors to VIP and GLP-1 and that they belong to a separate peptide family encoded by separate genes. Furthermore, the existence of as yet undiscovered mammalian homologues to Helodermin and exendin-4 seems unlikely.
-
molecular cloning of the Helodermin and exendin 4 cdnas in the lizard relationship to vasoactive intestinal polypeptide pituitary adenylate cyclase activating polypeptide and glucagon like peptide 1 and evidence against the existence of mammalian hom
Journal of Biological Chemistry, 1998Co-Authors: Markus Pohl, Stephen A. WankAbstract:Helodermin and exendin-4, two peptides isolated from the salivary gland of the Gila monster,Heloderma suspectum, are approximately 50% homologous to vasoactive intestinal peptide (VIP) and glucagon-like peptide-1 (GLP-1), respectively, and interact with the mammalian receptors for VIP and GLP-1 with equal or higher affinity and efficacy. Immunohistochemical studies suggested the presence of Helodermin-like peptides in mammals. To determine whether Helodermin and exendin-4 are present in mammals and their evolutionary relationship to VIP and GLP-1, their cDNAs were first cloned from Gila monster salivary gland. Northern blots and reverse transcription-polymerase chain reaction of multiple Gila monster tissues identified ∼500-base pair transcripts only from salivary gland. Both Helodermin and exendin-4 full-length cDNAs were ∼500 base pairs long, and they encoded precursor proteins containing the entire amino acid sequence of Helodermin and exendin-4, as well as a 44- or 45-amino acid N-terminal extension peptide, respectively, having ∼60% homology. The size and structural organization of these cDNAs indicated that they were closely related to one another but markedly different from known cDNAs for the VIP/GLP-1 peptide family previously identified in both lower and higher evolved species. Cloning of the Gila monster VIP/peptide histidine isoleucine, pituitary adenylate cyclase activating polypeptide, and glucagon/GLP-1 cDNAs and Southern blotting of Gila monster DNA demonstrate the coexistence of separate genes for these peptides and suggests, along with the restricted salivary gland expression, that Helodermin and exendin-4 coevolved to serve a separate specialized function. Probing of a variety of rat and human tissues on Northern blots, human and rat Southern blots, and genomic and cDNA libraries with either Helodermin- or exendin-4-specific cDNAs failed to identify evidence for mammalian homologues. These data indicate that Helodermin and exendin-4 are not the precursors to VIP and GLP-1 and that they belong to a separate peptide family encoded by separate genes. Furthermore, the existence of as yet undiscovered mammalian homologues to Helodermin and exendin-4 seems unlikely.
Victor Wray - One of the best experts on this subject based on the ideXlab platform.
-
NMR spectroscopic evidence that Helodermin, unlike other members of the secretin/VIP family of peptides, is substantially structured in water.
Biochemistry, 1996Co-Authors: Wulf Blankenfeldt, Satoru Naruse, Kiyoshi Nokihara, Uta Lessel, Dietmar Schomburg, Victor WrayAbstract:The structure in water and additionally in 50% trifluoroethanol (TFE) solution of Helodermin, an amidated peptide consisting of 35 amino acids, was elucidated by 2D 1H NMR spectroscopy initially from H alpha chemical shifts and qualitative NOE data. Detailed structures were calculated from the quantitative NOE data which were used as distance restraints in molecular dynamics and energy minimization calculations. Regions of stable secondary structure were defined from the resulting final peptide conformations using a new fitting program that takes into account the summed RMS differences between all structures for short segments of 2-5 residues in length. This procedure allows a reasonably objective method of defining the edges of stable structure. In contrast to other members of the secretin/VIP family of peptides, Helodermin shows a defined secondary structure in water alone and possesses an alpha-helix from Glu-9 to Leu-23 that was further stabilized and slightly extended (Phe-6 to Ala-24) on addition of TFE. The N- and C-termini were unstructured in both solutions. Such features, in particular the observation of a linear helix 18 +/- 2 residues in length, are common to other members of the family and become more pronounced in hydrophobic environments. The data provide further circumstantial evidence that an alpha-helix conformation is necessary for receptor binding. The prolonged physiological action of Helodermin, compared to its C-terminal deletion analogues and VIP, is at least in part due to the unusual stable secondary structure.
-
nmr spectroscopic evidence that Helodermin unlike other members of the secretin vip family of peptides is substantially structured in water
Biochemistry, 1996Co-Authors: Wulf Blankenfeldt, Satoru Naruse, Kiyoshi Nokihara, Uta Lessel, Dietmar Schomburg, Victor WrayAbstract:The structure in water and additionally in 50% trifluoroethanol (TFE) solution of Helodermin, an amidated peptide consisting of 35 amino acids, was elucidated by 2D 1H NMR spectroscopy initially from H alpha chemical shifts and qualitative NOE data. Detailed structures were calculated from the quantitative NOE data which were used as distance restraints in molecular dynamics and energy minimization calculations. Regions of stable secondary structure were defined from the resulting final peptide conformations using a new fitting program that takes into account the summed RMS differences between all structures for short segments of 2-5 residues in length. This procedure allows a reasonably objective method of defining the edges of stable structure. In contrast to other members of the secretin/VIP family of peptides, Helodermin shows a defined secondary structure in water alone and possesses an alpha-helix from Glu-9 to Leu-23 that was further stabilized and slightly extended (Phe-6 to Ala-24) on addition of TFE. The N- and C-termini were unstructured in both solutions. Such features, in particular the observation of a linear helix 18 +/- 2 residues in length, are common to other members of the family and become more pronounced in hydrophobic environments. The data provide further circumstantial evidence that an alpha-helix conformation is necessary for receptor binding. The prolonged physiological action of Helodermin, compared to its C-terminal deletion analogues and VIP, is at least in part due to the unusual stable secondary structure.