The Journal of Neuroscience, August 1, 1999, 19(15):6318-6326
Conformational Ensembles: The Role of Neuropeptide Structures in
Receptor Binding
Arthur S.
Edison,
Eduardo
Espinoza, and
Cherian
Zachariah
Department of Biochemistry and Molecular Biology, Center for
Structural Biology, University of Florida Brain Institute, and National
High Magnetic Field Laboratory, University of Florida, Gainesville,
Florida 32610-0245
Conformational properties of several similar FMRFamide-like
neuropeptides from mollusks were investigated by nuclear magnetic resonance (NMR) spectroscopy. It was found that amino acid
substitutions in the N-terminal variable regions of the peptides had
dramatic effects on the populations of reverse turns in solution. The
populations of turns, as measured by two independent NMR parameters,
were found to be highly correlated
(r2 = 0.93 and 0.82) with
IC50 values using receptor membrane preparations from
Helix aspersa (Payza, 1987; Payza et al., 1989). These
results suggest that the amount of turn in the free peptide can
influence the receptor binding affinities of that peptide. On the basis of these observations, a model was developed in which only a single species from a conformational ensemble of an unbound peptide will bind
to a particular receptor. Thus, the conformational ensemble reduces the effective concentration of a particular peptide with respect to a particular receptor.
Key words:
FMRFamide-like peptides; NMR; structure-function
relations; conformational averaging; dynamics; three-dimensional
structure; reverse turn
Copyright © 1999 Society for Neuroscience 0270-6474/99/19156318-09$05.00/0