Fungal Metabolites. XX. Effect of Proline Residue on the Structure of Ion-Channel-Forming Peptide, Trichosporin B-VIa.

Abstract

The secondary structures of an ion-channel-forming icosapeptaibol, trichosporin B-VIa, and its Aib14-substituted derivative containing no Pro were investigated on the basis of CD and various NM experiments in methanol. Trichosporin B-VIa has a fully helical structure with a kink stabilized by a 1<--4 hydrogen-bond between the Leu12 CO and Val15 NH. The helical structure is composed of 3(10)-helix in the N-terminal first turn and the C-terminal moiety following Leu12, and alpha-helix in the middle region. In contrast, the Aib14 derivative predominantly has a straight alpha-helical structure except for a 3(10)-helix region in the N-terminal first turn.