Mi. Liff et Ss. Siddiqui, NMR EVIDENCE OF FORMATION OF CYCLOCYSTINE LOOPS IN PEPTIDE MODELS OF THE HIGH-SULFUR PROTEINS FROM WOOL, International journal of biological macromolecules, 19(2), 1996, pp. 139-143
We report that in peptide models of the high sulfur proteins of the ma
trix from wool a disulfide bond forms between two sequential Cys-resid
ues as a result of a simple oxidation procedure. This tiny cyclocystin
e loop manifests itself in many ways in H-1 NMR spectra. The formation
of the loop is accompanied, as expected, by conversion of the Cys-Cys
peptide bond from its usual trans-configuration into the energeticall
y less favorable cis-configuration. Possible consequences of the forma
tion of cyclocystine loops for the elasticity of the network of the ma
trix are discussed.