Characterization of Helix Terminating Schellman Motifs in Peptides. Crystal Structure and Nuclear Overhauser Effect Analysis of a Synthetic Heptapeptide Helix

Datta, Saumen and Shamala, N and Banerjee, Arindam and Pramanik, Animesh and Bhattacharjya, Surajit and Balaram, P (1997) Characterization of Helix Terminating Schellman Motifs in Peptides. Crystal Structure and Nuclear Overhauser Effect Analysis of a Synthetic Heptapeptide Helix. In: Journal of the American Chemical Society, 119 (39). pp. 9246-9251.

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Abstract

The Schellman motif is a widely observed, helix terminating structural motif in proteins, which is achieved by the adoption of a left-handed helical (alphaL) conformation by a C-terminus residue. The resulting hydrogen bonding pattern involves an intramolecular 6 f 1 interaction. This helix terminating motif is readily mimicked in synthetic helical peptides by placing an achiral residue at the penultimate position of the helix. The crystal structure of the heptapeptide Boc-Leu-Aib-Val-Gly-Leu-Aib-Val-OMe (1) reveals a 310-helix terminated by a Schellman motif with Aib(6) adopting an alphaL - conformation. The crystals are in the space group P21 with a = 9.958(3)Å, b = 20.447-(3)Å, c = 11.723 (2)Å, beta = 99.74(2)°, and Z = 2. The final R1 and wR2 values are 7.2% and 18.9%, respectively, for 1731 observed reflections [I g 2Û(I)]. A 6 - 1 hydrogen bond between Aib(2)CO- - - -Val(7)NH and a 5 - 2 hydrogen bond between Val(3)CO- - - -Aib(6)NH are observed. An analysis of several alphaL terminated helical peptides in crystals suggests that the medium range CialphaH- - - -Ni+3H [dRN(i,i+3)] and CialphaH- - - -Ni+4H [dRN(i,i+4)] interproton distances are indeed characteristic of the Schellman motif. NMR studies in CDCl3 establish retention of the 310-helical conformation with key NOEs demonstrating the persistence of the conformation determined in crystals. The present study demonstrates the identification of the Schellman motif in solution in a synthetic helical peptide.

Item Type:	Journal Article
Publication:	Journal of the American Chemical Society
Publisher:	American Chemical Society
Additional Information:	Copyright for this article belongs to American Chemical Society.
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit Division of Physical & Mathematical Sciences > Physics
Date Deposited:	25 Oct 2004
Last Modified:	19 Sep 2010 04:16
URI:	http://eprints.iisc.ac.in/id/eprint/2192

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