# Crystal Structure of Boc-Ala-Aib-Ala-Aib-Aib-Methyl ester, A Pentapeptide Fragment of the Channel-Forming Ionophore Suzukacillin

Francis, AK and Iqbal, M and Balaram, P and Vijayan, M (1982) Crystal Structure of Boc-Ala-Aib-Ala-Aib-Aib-Methyl ester, A Pentapeptide Fragment of the Channel-Forming Ionophore Suzukacillin. In: Biopolymers, 22 (6). pp. 1499-1505.

 PDF full.pdf Restricted to Registered users only Download (386Kb) | Request a copy

## Abstract

t-Buthyoxycarbonyl-L-alanyl-\alpha-aminiosobutyryl-L-alanyl-\alpha-aminoisobutyryl-\alpha-aminoisobutyric acid methyl ester (t-Boc-L-Ala-Aib-L-Ala-Aib-Aib-OMe), $C_{24}H_{43}N_5O_8$, an end-protected pentapeptide with a sequence corresponding to the 6th through the 10th residues in suzukacillin, crystallizes in the orthorhombic space group $P2_12_12_1$ with a = 11.671, b = 14.534, c = 17.906 \AA and z = 4. The molecule exists as a right-handed $3_{10}-helix$ with a pitch of 6.026 \AA . The helix is stabilized by three 4 \longrightarrow 1 hydrogen bonds with the NH groups of Ala(3), Aib(4), and Aib(5) hydrogen bonding to the carbonyl oxygens of t-Boc, Ala(1), and Aib(2), respectively. The helical molecules arrange themselves in a head-to-tail fashion along the a direction in such a way that the NH groups of Ala(1) and Aib(2) hydrogen bond to the carbonyl oxygens of Aib(4) and Aib(5), respectively, of a translationally related molecule. The helical columns thus formed close-pack nearly hexagonally to form the crystal.

Item Type: Journal Article Copyright of this article belongs to John Wiley & Sons. Division of Biological Sciences > Molecular Biophysics Unit 03 Apr 2008 19 Sep 2010 04:44 http://eprints.iisc.ernet.in/id/eprint/13643