THE ROLE OF PRO20 IN THE ISOMERIZATION OF MYOTOXIN-A FROM CROTALUS-VIRIDIS-VIRIDIS - FOLDING AND STRUCTURAL CHARACTERIZATION OF SYNTHETIC MYOTOXIN-A AND ITS PRO20GLY HOMOLOG

Biochemical characterization has established the presence of two confo rmational forms of myotoxin a. To test the hypothesis that this may be due to cis-trans isomerization at Pro20, synthetic versions of myotox in a and its Pro20-->Gly structural homolog were folded, then purified using a two-step cation-exchange/reverse-phase perfusion chromatograp hy method. The disulfide bond configuration for the folded proteins wa s found to be the same as that of native myotoxin a CE and RP-HPLC rev ealed that folded synthetic myotoxin a exists in two conformations whi le the Pro20-->Gly homolog exists in only one, supporting the hypothes is that cis-trans isomerization at Pro20 is the source of the myotoxin a conformational heterogeneity. (C) 1997 Academic Press.