Conformational changes in four regions of the Escherichia coli ArsA ATPase link ATP hydrolysis to ion translocation.
Structures of ArsA with ATP, AMP-PNP, or ADP.AlF(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 ADP.AlF(3) provide insights into the mechanism of ATP hydrolysis. In-line attack by water onto the gamma-phosphate of ATP would be followed first by formation of a trigonal intermediate and then by breaking of the scissile bond between the beta- and gamma-phosphates. Motions of amino acid 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.
Zhou
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T
Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Michigan 48201, USA.
Radaev
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S
Rosen
B P
BP
Gatti
D L
DL
D000225:Adenine / Q000737:chemistry; D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000378:metabolism* / Q000502:physiology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D053501:Arsenite Transporting ATPases; D001665:Binding Sites; D001692:Biological Transport; D002384:Catalysis; D019281:Dimerization; D004926:Escherichia coli / Q000201:enzymology*; D006868:Hydrolysis; D016623:Ion Pumps; D007477:Ions; D007700:Kinetics; D008274:Magnesium / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D017386:Sequence Homology, Amino Acid; D014867:Water / Q000378:metabolism
D000596:Amino Acids; D016623:Ion Pumps; D007477:Ions; D009097:Multienzyme Complexes; D014867:Water; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D053501:Arsenite Transporting ATPases; D008274:Magnesium; D000225:Adenine