Parallel zippers formed by alpha-helical peptide columns in crystals of Boc-Aib-Glu(OBzl)-Leu-Aib-Ala-Leu-Aib-Ala-Lys(Z)-Aib-OMe

Karle, I. L. ; Flippen-Anderson, J. L. ; Uma, K. ; Balaram, P. (1990) Parallel zippers formed by alpha-helical peptide columns in crystals of Boc-Aib-Glu(OBzl)-Leu-Aib-Ala-Leu-Aib-Ala-Lys(Z)-Aib-OMe Proceedings of the National Academy of Sciences of the United States of America, 87 (20). pp. 7921-7925. ISSN 0027-8424

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Official URL: http://www.pnas.org/content/87/20/7921.short

Abstract

The crystal structure of the decapeptide Boc- Aib-Glu(OBzl)-Leu-Aib-Ala-Leu-Aib-Ala-Lys(Z)-Aib-OMe (where Aib is a-aminoisobutyryl, Boc is t-butoxycarbonyl, OBzI is benzyl ester, and Z is benzyloxycarbonyl) illustrates a parallel zipper arrangement of interacting helical peptide columns. Head-to-tail NH ... OC hydrogen bonding extends the a-helices formed by the decapeptide into long columns in the crystal. An additional NH ... OC hydrogen bond in the headto- tail region, between the extended side chains of Glu(OBzl), residue 2 in one molecule, and Lys(Z), residue 9 in another molecule, forms a "double tooth" on the side of the column. These double teeth are repeated regularly on the helical columns with spaces of six residues between them (≈ 10 A). The double teeth on a pair of parallel columns (all carbonyl groups pointed in the same direction) interdigitate in a zipper motif. All contacts in the zipper portion are of the van der Waals type. The peptide, with formula C66H103N11017.H20 crystallizes in space group P212121, with a = 10.677(4) Å, b = 16.452(6) Å, and c = 43.779(13) Å; overall agreement R = 10.2% for 3527 observed reflections (IF0I > 3σ); resolution 0.9 Å.

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Deposited On:18 Oct 2010 07:24
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