Metal ion binding affinities of gastrin and CCK in membrane mimetic environments

Lutz, Jürgen; Weyher, Elisabeth; Moröder, Luis

doi:10.1002/psc.310010603

Cited by 4 publications

References 47 publications

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Mapping of ligand binding sites of the cholecystokinin-B/gastrin receptor with lipo-gastrin peptides and molecular modeling

et al. 1997

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Double‐tailed lipo‐tetragastrin derivatives of increasing fatty acid chain length were used to identify the minimum size of the fatty acid moieties (≥C10) that restricts the access to the CCK‐B/gastrin (CCK: cholecystokinin) receptor via a membrane‐bound pathway. Then dimyristoyl‐mercaptoglycerol/maleoyl‐gastrin adducts of increasing peptide chain length were synthesized to define the minimal peptide size required for receptor binding affinities comparable to those of underivatized gastrin peptides despite anchorage of the lipid tails in the membrane bilayer. The experimental results indicated that most of the little‐gastrin sequence, i.e., 2–17, is needed for optimal interaction of the molecule with the binding cleft of the receptor. From these data experimentally based restraints could be derived for docking of lipo‐gastrin onto a CCK‐B/gastrin receptor model applying molecular dynamics simulations and energy minimizations. In the receptor‐bound state some of the secondary structure elements of gastrin as determined by nmr analysis of gastrin‐peptides in low dielectric constant media are retained. The N‐terminal gastrin portion interacts in a more or less extended conformation with the receptor surface, and upon a sharp kink at the Ala‐Tyr dipeptide portion the C‐terminal pentapeptide amide part inserts deeply into the helix bundle. Besides Arg‐57 on top of helix 1 of the receptor, for which no potential interaction with the ligand could be detected, the other amino acid residues identified by mutagenesis studies as involved in gastrin recognition were found to interact with the C‐terminal portion of gastrin. Even taking into account the strong limitations of such a model system, it represents an interesting tool for rationalizing the experimental results of the extensive structure‐function studies performed previously on gastrin and to delineate more precisely the putative ligand binding site on the extracellular face of the receptor. © 1997 John Wiley & Sons, Inc. Biopoly 41: 799–817, 1997

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Mapping of ligand binding sites of the cholecystokinin-B/gastrin receptor with lipo-gastrin peptides and molecular modeling

et al. 1997

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On the Mechanism of Hormone Recognition and Binding by the CCK-B/Gastrin Receptor

Moröder

1997

J. Peptide Sci.

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Lipidation with long-chain di-fattyacyl-glycerol moieties was used to anchor gastrin in CCK peptides irreversibly to lipid bilayers lipopeptide transfer to model phospholipid bilayers is fast and quantitative, leading to a different mode of insertion of lipo-gastrin and lipo-CCK in lipid layers. Lipo-gastrin remains exposed to the bulk solvent in a predominantly random coil structure as a consequence of electrostatic repulsion, whereas lipo-CCK exhibits a pronounced tendency to form peptide domains with insertion of its C-terminus into more hydrophobic compartments of the bilayers. Thereby Ca2+ at physiological concentrations favours this aggregational phenomenon. Since both lipo-peptides were found to retain almost full receptor affinity despite their irreversible anchorage to the bilayer, a membrane-bound pathway in the receptor recognition and binding process is indeed possible. According to the data collected in this study, CCK might possibly use this pathway, whereas accumulation of gastrin on the cell membrane with prefolding of the ligand at the water/lipid interface is hardly conceivable. Nevertheless the observed receptor interaction of the deliberately membrane-anchored gastrin offers interesting constraints for computational docking experiments on a modelled CCK-B/gastrin receptor by additionally taking into account information derived from mutagenesis studies. Despite the limitations of such modelling experiments, the resulting picture of the gastrin/receptor complex allowed the visualization and rationalization of the experimental results of the extensive structure-function studies performed previously on this family of gastrointestinal hormones.

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Overexpression of Proteins with Seven Transmembrane Spanning Segments

Hildebrandt¹,

Oesterhelt²

1997

Foreign Gene Expression in Fission Yeast: Schizosaccharomyces Pombe

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Metal ion binding affinities of gastrin and CCK in membrane mimetic environments

Cited by 4 publications

References 47 publications

Mapping of ligand binding sites of the cholecystokinin-B/gastrin receptor with lipo-gastrin peptides and molecular modeling

Mapping of ligand binding sites of the cholecystokinin-B/gastrin receptor with lipo-gastrin peptides and molecular modeling

On the Mechanism of Hormone Recognition and Binding by the CCK-B/Gastrin Receptor

Overexpression of Proteins with Seven Transmembrane Spanning Segments

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