1jqe

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Revision as of 15:37, 12 November 2007

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spinqualitylabelsall models 1jqe, resolution 1.91Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Crystal Structure Analysis of Human Histamine Methyltransferase (Ile105 Polymorphic Variant) Complexed with AdoHcy and Antimalarial Drug Quinacrine

Contents 1 Overview 2 Disease 3 About this Structure 4 Reference

Overview

BACKGROUND: Histamine plays important biological roles in cell-to-cell, communication; it is a mediator in allergic responses, a regulator of, gastric acid secretion, a messenger in bronchial asthma, and a, neurotransmitter in the central nervous system. Histamine acts by binding, to histamine receptors, and its local action is terminated primarily by, methylation. Human histamine N-methyltransferase (HNMT) has a common, polymorphism at residue 105 that correlates with the high- (Thr) and low-, (Ile) activity phenotypes. RESULTS: Two ternary structures of human HNMT, have been determined: the Thr105 variant complexed with its substrate, histamine and reaction product AdoHcy and the Ile105 variant complexed, with an inhibitor (quinacrine) and AdoHcy. Our steady-state kinetic data, indicate that the recombinant Ile105 variant shows 1.8- and 1.3-fold, increases in the apparent K(M) for AdoMet and histamine, respectively, and, slightly (16%) but consistently lower specific activity as compared to, that of the Thr105 variant. These differences hold over a temperature, range of 25 degrees C-45 degrees C in vitro. Only at a temperature of 50, degrees C or higher is the Ile105 variant more thermolabile than the, Thr105 enzyme. CONCLUSIONS: HNMT has a 2 domain structure including a, consensus AdoMet binding domain, where the residue 105 is located on the, surface, consistent with the kinetic data that the polymorphism does not, affect overall protein stability at physiological temperatures but lowers, K(M) values for AdoMet and histamine. The interactions between HNMT and, quinacrine provide the first structural insights into a large group of, pharmacologic HNMT inhibitors and their mechanisms of inhibition.

Disease

Known disease associated with this structure: Asthma, susceptibility to OMIM:[605238]

About this Structure

1JQE is a Single protein structure of sequence from Homo sapiens with SAH, QUN and UNX as ligands. Active as Histamine N-methyltransferase, with EC number 2.1.1.8 Full crystallographic information is available from OCA.

Reference

Two polymorphic forms of human histamine methyltransferase: structural, thermal, and kinetic comparisons., Horton JR, Sawada K, Nishibori M, Zhang X, Cheng X, Structure. 2001 Sep;9(9):837-49. PMID:11566133

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