Arg-conopressin-S and Lys-conopressin-G are cyclic disulphide-bridged nonapeptides
isolated from the venom of cone snails. We performed a comprehensive conformational
analysis for the cis and trans isomers of these conopeptides, in order to identify
their characteristic structural and conformational features. In the course of our
theoretical study, the Phi-Psi and chi(1) conformational spaces were explored in detail
and the conformational distributions were compared to each other. For both cis and
trans isomers of conopressins, the characteristic secondary structural elements and
intramolecular H-bonds were identified. Our results pointed out that various turn
structures stabilized by typical intramolecular H-bonds could be observed in the conformers
of these conopeptides. Comparing the different conformational features of the cis
and trans isomers of conopressins disclosed that several of them could be found for
both isomers, however, structural properties characteristic for only the cis or trans
isomer were also identified. Altogether, our comprehensive conformational study provided
a detailed description of the three-dimensional (3D) structure of both conopressins.
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