Modulation of Alpha-Subunit VISIT-DG Sequence Residues Ser-347, Gly-351 and Thr-349 in the Catalytic Sites of \u3cem\u3eEscherichia coli\u3c/em\u3e ATP Synthase.

Abstract

Binding of inorganic phosphate (Pi) in ATP synthase catalytic sites is a crucial step for the synthesis of adenosine-5\u27-triphosphate (ATP). ATP is the fundamental means of cellular energy in almost every organism, and in order to gain insight into the regulation of ATP catalysis, critical amino acid residues responsible for binding Pi must be identified. Here, we investigate the role of highly conserved α-subunit VISIT-DG sequence residues αSer-347, αGly-351, and αThr-349 in Pi binding. Mutations αS347A/Q, αG351Q, αT349A/D/R, βR182A, and αT349R/βR182A were generated via site directed mutagenesis. Results from biochemical assays showed that αSer-347 is required for transition state stabilization and Pi binding whereas αGly-351 is only indirectly involved in Pi binding and most likely maintains structural integrity of the catalytic site. Results from preliminary experiments on αThr-349 mutants suggest that the residue may be involved in Pi binding; however, further investigation is required to fully test this hypothesis