Beta-turn mimic in tripeptide with Phe(1)-Aib(2) as corner residues and beta-strand structure in an isomeric tripeptide: an X-ray diffraction study.
A single crystal X-ray diffraction study of the tripeptide Boc-Phe-Aib-Leu-OMe (Aib = alpha-aminoisobutyric acid) reveals that it forms structurally one of the best type II beta-turns so far reported in tripeptides, stabilized by 10 atom intramolecular hydrogen bonding. In contrast, the isomeric tripeptide Boc-Phe-Leu-Aib-OMe adopts a beta-strand like conformation. Interestingly, a previously reported structure of another isomeric tripeptide, Boc-Leu-Aib-Phe-OMe, shows a double bend conformation without any intramolecular hydrogen bonding. These results demonstrate an example of the creation of structural diversities in the backbone of small peptides depending upon the co-operative steric interactions amongst the amino acid residues.
Dutt
Anita
A
Department of Chemistry, University of Calcutta, 92, A. P. C. Road, Kolkata 700 009, India.
Fröhlich
Roland
R
Pramanik
Animesh
A
D000621:Aminoisobutyric Acids / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005563:Formic Acid Esters / Q000737:chemistry; D006860:Hydrogen Bonding; D007930:Leucine / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry*; D010649:Phenylalanine / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary
D000621:Aminoisobutyric Acids; D005563:Formic Acid Esters; D009842:Oligopeptides; C000345:t-butyloxycarbonyl group; D010649:Phenylalanine; D007930:Leucine