Meyer S, Drewello M, Fischer G
Max-Planck-Gesellschaft, Arbeitsgruppe, Enzymologie der Peptidbindung, Halle/Saale, Germany.
Biol Chem. 1996 Jul-Aug;377(7-8):489-95.
The trifluoroethanol (TFE)-induced formation of alpha-helical structures in the peptide hormone calcitonin (salmon) was studied using limited proteolysis combined with capillary zone electrophoresis. A low TFE content in TFE/buffer mixtures was insufficient to introduce secondary structure, but two Lys-Leu bonds were found to have become inaccessible to proteolysis with clostripain. The influence of increasing helical degree of the Thr6-Lys18 (or Thr6-Tyr22 in the trans conformation) segment on the cis/trans isomerization of the adjacent Tyr22-Pro23 peptide bond was examined by means of isomer specific proteolysis. Results indicate that the helix dipole does not influence the cis/trans equilibrium distribution of the flanking Tyr22-Pro23 bond but considerably increases its isomerization rate Ko-->t.
