Datta, Saumen ; Shamala, N. ; Banerjee, Arindam ; Pramanik, Animesh ; Bhattacharjya, Surajit ; Balaram, P. (1997) Characterization of helix terminating schellman motifs in peptides. Crystal structure and nuclear overhauser effect analysis of a synthetic heptapeptide helix Journal of the American Chemical Society, 119 (39). pp. 9246-9251. ISSN 0002-7863
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Official URL: http://pubs.acs.org/doi/abs/10.1021/ja970551y
Related URL: http://dx.doi.org/10.1021/ja970551y
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 (αL) conformation by a C-terminus residue. The resulting hydrogen bonding pattern involves an intramolecular 6 → 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 αL - 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, β = 99.74(2)°, and Z = 2. The final R1 and wR2 values are 7.2% and 18.9%, respectively, for 1731 observed reflections [I ≥ 2σ(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 αL terminated helical peptides in crystals suggests that the medium range CiαH----Ni+3H [dαN(i,i+3)] and CiαH----Ni+4H [dαNN(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: | Article |
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Source: | Copyright of this article belongs to American Chemical Society. |
ID Code: | 4509 |
Deposited On: | 18 Oct 2010 07:38 |
Last Modified: | 11 May 2012 10:06 |
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