CONFORMATIONAL ASPECTS OF THE INTERACTION OF BRADYKININ AND RELATED PEPTIDES WITH SODIUM DODECYL-SULFATE

Conformational aspects of the interaction of SDS with bradykinin (BK) and related peptides were probed by CD, 1H, 13C, and 19F NMR. The spectrum of [99% 13C-2-Gly6]bradykinin, pH 8.3, confirmed the high cis/trans ratio about the sixth peptide bond. Addition of 5.2 mM SDS broadened both the cis and trans 13C resonances but only shifted the trans. Moreover, the cis/trans ratio increased substantially. Thus, the cis isomer is enhanced in the complex. 19F NMR of [Gly6,p-fluoro-Phe8] bradykinin indicated that the p-fluoro-Phe8 also sensed the cis and trans isomers of Pro7. Addition of the same molar ratio of SDS:BK analogue as used for [13C-2-Gly6]BK gave a spectrum showing a similar increase in cis/trans ratio, but the cis 19F NMR peak was shifted the most. The strong interactions of monomeric SDS with bradykinin and its C-terminal tetrapeptide fragment, SerProPheArg, were reflected in a generalized broadening of all signals accompanied by selective shifts and changes in coupling constants of some resonances. For the trans conformer of SerProPheArg the significantly shifted resonances were α- and β-Ser, (βt- and γt-Pro, and the ring protons of Phe. Previous and current CD spectra also indicated changes in conformation upon interaction with SDS. The presence of selective shifts of the NMR resonances bears upon the interpretation of the CD bands. © 1990, American Chemical Society. All rights reserved.