Conformational Interconversions of the Cyclic Hexapeptide Cyclo(Pro-Gly)3*†

AUTOR(ES)

Deber, Charles M.

RESUMO

A cyclic hexapeptide, cyclo(Pro-Gly-Pro-Gly-Pro-Gly), has been synthesized; its solution conformations were examined by 220-MHz nuclear magnetic resonance spectroscopy. The solution structures have been deduced, and shown to vary as a function of solvent polarity. In addition, it has been found that this cyclic peptide binds alkali metal cations. While the predominant conformation of this cyclic peptide is 3-fold symmetric in the apolar solvent methylene chloride, an asymmetric structure is preferred in some polar solvents (water, dimethylsulfoxide). However, addition of alkali metal salts, such as sodium thiocyanate, to dimethylsulfoxide solutions of the peptide shifts the conformational equilibrium in favor of a second type of C3-symmetric structure, presumably the result of the formation of a stable peptide-metal ion complex. Nuclear magnetic resonance data suggest that the peptide in methylene chloride solution takes up a conformation containing three cis′ Pro Cα-C=O bonds and three cis Gly-Pro peptide bonds; that water and dimethylsulfoxide stabilize a conformer in which one (or two) sets of such bonds of a given Pro-Gly unit have undergone interconversion to trans′/trans forms; and that alkali metal cations complex the cyclic peptide in a C3-symmetric all-trans′/trans structure.

Documentos Relacionados

• Conformation of cyclo(Gly-L-Pro-L-Pro-Gly-L-Pro-L-Pro)2Mg2+ complex crystallized from C2H3CN solution
• Conformation of cyclo(-L-Pro-Gly-)3 and its Ca2+ and Mg2+ complexes
• On the ion selectivity in Ca-binding proteins: the cyclo(-L-Pro-Gly-)3 peptide as a model.
• Lactobacillus plantarum MiLAB 393 Produces the Antifungal Cyclic Dipeptides Cyclo(l-Phe-l-Pro) and Cyclo(l-Phe-trans-4-OH-l-Pro) and 3-Phenyllactic Acid
• Synthetic hexapeptide substrates and inhibitors of 3':5'-cyclic AMP-dependent protein kinase.