Open AccessLong polypeptide 3 10 -helices at atomic resolution
Author(s) -
Alfonso Bavoso,
Ettore Benedetti,
Benedetto Di Blasio,
Vincenzo Pavone,
Carlo Pedone,
Claudio Toniolo,
Gian Maria Bonora
Publication year - 1986
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.83.7.1988
Subject(s) - intramolecular force , chemistry , hydrogen bond , peptide , crystallography , stereochemistry , helix (gastropod) , residue (chemistry) , crystal structure , amino acid , peptide sequence , sequence (biology) , molecule , biochemistry , biology , ecology , organic chemistry , snail , gene
The crystal-state preferred conformation of the terminally blocked homooctapeptide from the Cα,α -dimethylated α-aminoisobutyric acid (Aib) residue,p BrBz-(Aib)8 -OBut , in whichp BrBz ispara -bromobenzoyl and OBut istert -butoxy, determined by x-ray diffraction analysis using direct methods, was found to be a 310 -helix stabilized by six consecutive intramolecular N—H....O=C hydrogen bonds of the C10 -III (or III′) type. This is the first observation at atomic resolution of a regular 310 -helix longer than two complete turns. The solid-state structural analysis was extended to the terminally blocked, α-aminoisobutyric acid-rich octapeptide corresponding to the 2-9 sequence of the peptaibol antibiotics emerimicins III and IV,p BrBz-Aib3 -L-Val-Gly-L-Leu-Aib2 -OMe. Again, this peptide adopts a (right-handed) 310 -helical structure, although slightly distorted at the level of the L-leucine residue. The role of specific amino acid sequence and peptide main-chain length in stabilizing either the 310 - or the α-helical conformation and their possible implications on the nature of the channel formed by peptaibol antibiotics in the membrane are also briefly discussed.