The crystal structures of [Met5]enkephalin and a third form of [Leu5]enkephalin: observations of a novel pleated beta-sheet.

Abstract

The structures of [Met5]enkephalin (Tyr-GlyGly-Phe-Met) and [Leu5]enkephalin (Tyr-Gly-Gly-Phe-Leu) have been determined from single crystal x-ray diffraction data and refined to residuals of 0.100 and 0.092, respectively. The [Met5]enkephalin structure consists of dimers forming antiparallel a-sheets extending in the monoclinic ac plane with 10.6 water molecules per dimer. The two molecules, related by pseudo two-fold axes, have similar backbone conformations and similar tyrosine and phenylalanine side-chain conformations. Both methionine residues are disordered and the disorder is different in the two independent molecules. Additional hydrogen bonds connect adjacent dimers to form infinite sheets normal to the b axis. The water molecules are found mainly in the interstices between the sheets. [Leu5]Enkephalin crystallizes as a monohydrate that is isomorphous with the [Met5]enkephalin structure with respect to the a-sheet but different with respect to the tyrosine and phenylalanine side-chain conformations and water content. The peptide chains in both structures are fully extended and more nearly planar than pleated. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

Structural and spectroscopic analysis of hydrogensquarates of glycine‐containing tripeptides

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Solid‐state IR–LD spectroscopic and theoretical analysis of glycine‐containing peptides and their hydrochlorides

“…Optimized values of GG, GGG, and their protonated forms (GGH and GGGH) agree reasonably well with those refined by X-ray diffraction for the compound studied [16][17][18][19] and other tripeptides having glycine residues. 8,[20][21][22] Comparing both experimental and theoretical data, the atomic distances and angles do not differ by more than 0.009 Å and 3.4 (5) o .…”

Exploring the Backbone of Enkephalins To Adjust Their Pharmacological Profile for the δ-Opioid Receptor

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