A helical peptide containing a majority of valyl residues. The crystal structure of t-butyloxy- carbonyl-(L-valyl-_-aminoisobutyryl)3-L-valyl methyl ester onohydrate

Vijayan, M and Balaram, Padmanabhan and Francis, AK and Vijayakumar, EKS (1985) A helical peptide containing a majority of valyl residues. The crystal structure of t-butyloxy- carbonyl-(L-valyl-_-aminoisobutyryl)3-L-valyl methyl ester onohydrate. In: International Journal of Peptide and Protein Research, 26 (2). pp. 214-223.

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Abstract

The monohydrate of the heptapeptide t-butyloxycarbonyl-(L-valyl-α-aminoiso-butyryl)3-L-valyl methyl ester crystallizes in the orthorhombic space group P212121 with four molecules in a unit cell with the dimensions α= 9.375, b = 19.413 and c = 25.878 ÅA. The structure has been solved by direct methods and refined to an R value of 0.059 for 3633 observed reflections. The molecule in the structure exists as a slightly distorted 310-helix stabilized by five 4 -> 1 intramolecular hydrogen bonds, indicating the overwhelming influence of α-aminoisobutyryl (Aib) residues in dictating helical fold even when a majority of residues in the peptide have a low intrinsic propensity to be in helices. Contrary to what is expected in helical structures, the valyl side chains, two of which are disordered, exhibit all three possible conformations. The molecules arrange themselves in a head-to-tail fashion along the c-axis. The columns thus generated pack nearly hexagonally in the crystal.

Item Type:	Journal Article
Publication:	International Journal of Peptide and Protein Research
Publisher:	John Wiley & Sons
Additional Information:	Copyright of this article belongs to John Wiley & Sons.
Keywords:	Aib peptide; channel forming ionophores; 310 -helix; heptapeptide; X-ray crystallography.
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	09 Nov 2010 09:21
Last Modified:	09 Nov 2010 09:21
URI:	http://eprints.iisc.ac.in/id/eprint/33484

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