Table of Contents
Journal of Amino Acids
Volume 2011 (2011), Article ID 785741, 12 pages
http://dx.doi.org/10.4061/2011/785741
Review Article

Role of Charged Residues in the Catalytic Sites of Escherichia coli ATP Synthase

1Department of Biology, Alabama A&M University, P.O. Box 610, Normal, AL 35762, USA
2Department of Biological Sciences, East Tennessee State University, Johnson City, TN 37614, USA

Received 15 February 2011; Accepted 21 April 2011

Academic Editor: Faizan Ahmad

Copyright © 2011 Zulfiqar Ahmad et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Here we describe the role of charged amino acids at the catalytic sites of Escherichia coli ATP synthase. There are four positively charged and four negatively charged residues in the vicinity of of E. coli ATP synthase catalytic sites. Positive charges are contributed by three arginine and one lysine, while negative charges are contributed by two aspartic acid and two glutamic acid residues. Replacement of arginine with a neutral amino acid has been shown to abrogate phosphate binding, while restoration of phosphate binding has been accomplished by insertion of arginine at the same or a nearby location. The number and position of positive charges plays a critical role in the proper and efficient binding of phosphate. However, a cluster of many positive charges inhibits phosphate binding. Moreover, the presence of negatively charged residues seems a requisite for the proper orientation and functioning of positively charged residues in the catalytic sites. This implies that electrostatic interactions between amino acids are an important constituent of initial phosphate binding in the catalytic sites. Significant loss of function in growth and ATPase activity assays in mutants generated through charge modulations has demonstrated that precise location and stereochemical interactions are of paramount importance.