Long, chiral polypeptide 3(10)-helices at atomic resolution.
The crystal-state preferred conformation of the terminally blocked hepta- and octapeptides with the general formula -(Aib)n L-Leu-(Aib)2- (n = 4 and 5, respectively), determined by X-ray diffraction, was found to be a right-handed 3(10)-helix stabilized by five and six consecutive intramolecular NH...O = C H-bonds of the C(10)-III type, respectively. The octapeptide structure represents the first observation at atomic resolution of a regular, chiral 3(10)-helix larger than two complete turns. In both cases the right handed screw sense of the helix is dictated by the presence of the single, internal L-residue. This study confirms the propensity of short peptides rich in Aib, the prototype of the amino acid residues dialkylated at the alpha carbon, to adopt a 3(10)-helical structure and is expected to help our understanding of the conformational preferences of the membrane-active, channel-forming, ion-transporting peptaibol antibiotics.
Bavoso
A
A
Department of Chemistry, University of Napoli, Italy.
Benedetti
E
E
Di Blasio
B
B
Pavone
V
V
Pedone
C
C
Toniolo
C
C
Bonora
G M
GM
Formaggio
F
F
Crisman
M
M
D002087:Butyrates / Q000138:chemical synthesis; D006860:Hydrogen Bonding; D007930:Leucine / Q000031:analogs & derivatives / Q000138:chemical synthesis; D008958:Models, Molecular; D010455:Peptides / Q000138:chemical synthesis; D011487:Protein Conformation; D014961:X-Ray Diffraction
D002087:Butyrates; D010455:Peptides; C062977:4-bromobenzoyl-(alpha-aminoisobutyric acid)(5)-leucyl-(alpha-aminoisobutyric acid)(2)-methoxy; D007930:Leucine