Stabilization of a novel β-turn-like motif by nonconventional intramolecular hydrogen-bonding interactions in a model peptide incorporating β-alanine

✍ Scribed by A. K. Thakur; R. Kishore

• Publisher: Wiley (John Wiley & Sons)
• Year: 2000
• Tongue: English
• Weight: 119 KB
• Volume: 53
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/(sici)1097-0282(200005)53:6<447::aid-bip1>3.0.co;2-h

✦ Synopsis

The chemical synthesis and x-ray crystal structure analysis of a model peptide incorporating a conformationally adaptable unsubstituted ␤-Ala residue: Boc-␤-Ala-Acc 6 -OCH 3 (C 16 H 28 N 2 O 5 , molecular weight ϭ 328.41; 1) has been described. The peptide crystallized in the space group P2 1 2 1 2 1 a ϭ 8.537 (3), b ϭ 8.872 (10), c ϭ 25.327 (8), ␣ ϭ ␤ ϭ ␥ ϭ 90.0°, Z ϭ 4. An attractive feature of the crystal structure analysis of 1 is an accommodation of a significantly folded ␤-Ala residue in a short linear peptide. The overall peptide conformation is typically folded into a ␤-turn-like motif. The stabilization of the peptide backbone conformation by nonconventional COH . . . O weak intramolecular hydrogen-bonding interactions, involving the ester terminal carbon atom and the ethereal oxygen of the Boc group, has been evoked. The conformational constraint that seems most apparent is the , value of the highly constrained hydrophobic Acc 6 ring that may play a key role in inducing or sustaining the observed pseudo type III or IIIЈ ␤-turn structure. The resulting 12-membered hydrogen bonding ring motif in 1 is distinctly different from the one found in classical ␤-turn structures, stabilized by a conventional strong CAO . . . HON intramolecular hydrogen bond, comprised of ␣-amino acids. The potential of the conformationally adaptable ␤-Ala residue to occupy i ϩ 1 position (left corner) of the folded ␤-turn-like structure and to design and construct novel secondary structural features have been emphasized.