Conformational Changes in Four Regions of theEscherichia coliArsA ATPase Link ATP Hydrolysis to Ion Translocation

Tongqing Zhou, Sergei Radaev, Barry P. Rosen, Domenico L. Gatti
2001 Journal of Biological Chemistry  
Structures of ArsA with ATP, AMP-PNP, or ADP⅐AlF 3 bound at the A2 nucleotide binding site were determined. Binding of different nucleotides modifies the coordination sphere of Mg 2؉ . In particular, the changes elicited by ADP⅐AlF 3 provide insights into the mechanism of ATP hydrolysis. In-line attack by water onto the ␥-phosphate of ATP would be followed first by formation of a trigonal intermediate and then by breaking of the scissile bond between the ␤and ␥-phosphates. Motions of amino acid
more » ... side chains at the A2 nucleotide binding site during ATP binding and hydrolysis propagate at a distance, producing conformational changes in four different regions of the protein corresponding to helices H4 -H5, helices H9 -H10, helices H13-H15, and to the S1-H2-S2 region. These elements are extensions of, respectively, the Switch I and Switch II regions, the A-loop (a small loop near the nucleotide adenine moiety), and the P-loop. Based on the observed conformational changes, it is proposed that ArsA functions as a reciprocating engine that hydrolyzes 2 mol of ATP per each cycle of ion translocation across the membrane.
doi:10.1074/jbc.m103671200 pmid:11395509 fatcat:mvzgbw5k4zfztjy2oilr2i7ixe