Tryptophan-containing peptide helices: Interactions involving the indole side chain

Mahalakshmi, R. ; Sengupta, A. ; Raghothama, S. ; Shamala, N. ; Balaram, P. (2005) Tryptophan-containing peptide helices: Interactions involving the indole side chain The Journal of Peptide Research, 66 (5). pp. 277-296. ISSN 1397-002X

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Two designed peptide sequences containing Trp residues at positions i and i + 5 (Boc-Leu-Trp-Val-Ala-Aib-Leu-Trp-Val-OMe, 1) as well as i and i + 6 (Boc-Leu-Trp-Val-Aib-Ala-Aib-Leu-Trp-Val-OMe, 2) containing one and two centrally positioned Aib residues, respectively, for helix nucleation, have been shown to form stable helices in chloroform solutions. Structures derived from nuclear magnetic resonance (NMR) data reveal six and seven intramolecularly hydrogen-bonded NH groups in peptides 1 and 2, respectively. The helical conformation of octapeptide 1 has also been established in the solid state by X-ray diffraction. The crystal structure reveals an interesting packing motif in which helical columns are stabilized by side chain-backbone hydrogen bonding involving the indole Nε1H of Trp(2) as donor, and an acceptor C=O group from Leu(6) of a neighboring molecule. Helical columns also associate laterally, and strong interactions are observed between the Trp(2) and Trp(7) residues on neighboring molecules. The edge-to-face aromatic interactions between the indoles suggest a potential C-H…π interaction involving the Cζ3H of Trp(2). Concentration dependence of NMR chemical shifts provides evidence for peptide association in solution involving the Trp(2) Nε1H protons, presumably in a manner similar to that observed in the crystal.

Item Type:Article
Source:Copyright of this article belongs to John Wiley and Sons, Inc.
Keywords:Aromatic Interactions; C-H…π Interactions; Indole NH Hydrogen Bonding; Nuclear Magnetic Resonance Structures; Peptide Aggregation; Tryptophan Peptides
ID Code:4752
Deposited On:18 Oct 2010 06:50
Last Modified:16 May 2016 15:21

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