1ii9: Difference between revisions

[[Image:1ii9.gif|left|200px]]<br /><applet load="1ii9" size="350" color="white" frame="true" align="right" spinBox="true"  

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.

1II9 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=MG:'>MG</scene>, <scene name='pdbligand=CD:'>CD</scene>, <scene name='pdbligand=CL:'>CL</scene>, <scene name='pdbligand=ADP:'>ADP</scene>, <scene name='pdbligand=ANP:'>ANP</scene> and <scene name='pdbligand=TAS:'>TAS</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Arsenite-transporting_ATPase Arsenite-transporting ATPase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.6.3.16 3.6.3.16] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1II9 OCA].  

[[Category: Gatti, D L.]]

[[Category: Rosen, B P.]]

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