Conformation of a 16-residue zervamicin IIA analog peptide containing three different structural features: 3(10)-helix, alpha-helix, and beta-bend ribbon.

Publisher Website
Google Scholar
Abstract
Boc-Trp-Ile-Ala-Aib-Ile-Val-Aib-Leu-Aib-Pro-Ala-Aib-Pro-Aib-Pro-Phe-OMe (where Boc is t-butoxycarbonyl and Aib is .alpha.-aminoisobutyric acid), a synthetic apolar analog of the membrane-active fungal peptide antibiotic aervamycin IIA, crystallizes in space group P1 with Z = 1 and cell parameters a = 9.086 .+-. 0.002 AANG, b = 10.410 .+-. 0.002 AANG, c = 28.188 .+-. 0.004 AANG, .alpha. = 86.13 .+-. 0.01.degree., .beta. = 87.90 .+-. 0.01.degree., and .gamma. = 89.27 .+-. 0.01.degree.; overall agreement factor R = 7.3% for 7180 data (F0 > 3.sigma.) and 0.91-AANG resolution. The peptide backbone makes a continuous spiral that begins as 310-helix at the N-terminus, changes to an .alpha.-helix for two turns, and ends in a spiral of three .beta.-bends in a ribbon. Each of the .beta.-bends contains a proline residue at one of the corners. The torsion angles S.phi.i range from -51.degree. to -91.degree. (average value -64.degree.), and the torsion angles .psi.i range from -1.degree. to -46.degree. (average value 131.degree.). There are 10 intramolecular NH .cntdot..cntdot..cntdot. OC hydrogen bonds in the hilix and two direct head-to-tail hydrogen bonds between successive molecules. Two H2O and two CH3OH solvent molecules fill additional space with appropriate hydrogen bonding in the head-to-tail region, and two additional H2O molecules form hydrogen bonds with carbonyl oxygen near the curve in the helix at Pro-10. Since there is only one peptide molecule per cell in space group P1, the molecules repeat only by translation, and consequently the helicies pack parallel to each other.