Campus Units

Biochemistry, Biophysics and Molecular Biology

Document Type

Article

Publication Version

Published Version

Publication Date

2002

Journal or Book Title

The Journal of Biological Chemistry

Volume

277

Issue

11

First Page

8817

Last Page

8821

DOI

10.1074/jbc.M111810200

Abstract

Adenylosuccinate synthetase governs the first committed step in the de novo synthesis of AMP. Mutations of conserved residues in the synthetase fromEscherichia coli reveal significant roles for Val273 and Thr300 in the recognition ofL-aspartate, even though these residues do not or cannot hydrogen bond with the substrate. The mutation of Thr300 to alanine increases the K m forL-aspartate by 30-fold. In contrast, its mutation to valine causes no more than a 4-fold increase in the K m forL-aspartate, while increasing k catby 3-fold. Mutations of Val273 to alanine, threonine, or asparagine increase the K m forL-aspartate from 15- to 40-fold, and concomitantly decrease the K ifor dicarboxylate analogues ofL-aspartate by up to 40-fold. The above perturbations are comparable with those resulting from the elimination of a hydrogen bond between the enzyme and substrate: alanine mutations of Thr128 and Thr129 increase theK m for IMP by up to 30-fold and the alanine mutation of Thr301 abolishes catalysis supported byL-aspartate, but has no effect on catalysis supported by hydroxylamine. Structure-based mechanisms, by which the above residues influence substrate recognition, are presented.

Comments

This research was originally published in The Journal of Biological Chemistry. Andrea Gorrell, Wenyan Wang, Eric Underbakke, Zhenglin Hou, Richard B. Honzatko, and Herbert J. Fromm. Determinants of L-Aspartate and IMP Recognition in Escherichia coli Adenylosuccinate Synthetase. The Journal of Biological Chemistry. 2002; 277:8817-8821. © the American Society for Biochemistry and Molecular Biology.

Copyright Owner

The American Society for Biochemistry and Molecular Biology, Inc.

Language

en

File Format

application/pdf

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