A helical peptide containing a majority of valyl residues
Crystal structure of t-butyloxycarbonyl-(L-valyl-α-aminoisobutyryl)3-L-valyl methyl ester monohydrate
Article first published online: 12 JAN 2009
© 1985 Munksgaard International Publishers Ltd.
International Journal of Peptide and Protein Research
Volume 26, Issue 2, pages 214–223, August 1985
How to Cite
FRANCIS, A.K., VIJAYAKUMAR, E.K.S., BALARAM, P. and VIJAYAN, M. (1985), A helical peptide containing a majority of valyl residues. International Journal of Peptide and Protein Research, 26: 214–223. doi: 10.1111/j.1399-3011.1985.tb03199.x
- Issue published online: 12 JAN 2009
- Article first published online: 12 JAN 2009
- Recieved 17 October 1984 accepted 15 February 1985
- Aib peptide;
- channel forming ionophores;
- 310 -helix;
- X-ray crystallography
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.