Role of conserved histidine residues in metalloactivation of the ArsA ATPase.
The ArsA ATPase is the catalytic subunit of a pump that is responsible for resistance to arsenicals and antimonials in Escherichia coli. Arsenite or antimonite allosterically activates the ArsA ATPase activity. ArsA homologues from eubacteria, archaea and eukarya have a signature sequence (DTAPTGHT) that includes a conserved histidine. The ArsA ATPase has two such conserved motifs, one in the NH2-terminal (Al) half and the other in the COOH-terminal (A2) half of the protein. These sequences have been proposed to be signal transduction domains that transmit the information of metal occupancy at the allosteric to the catalytic site to activate ATP hydrolysis. The role of the conserved residues His148 and His453, which reside in the A1 and A2 signal transduction domains respectively, was investigated by mutagenesis to create H148A, H453A or H148A/H453A ArsAs. Each altered protein exhibited a decrease in the Vmax of metalloid-activated ATP hydrolysis, in the order wild type ArsA>H148A>H453A>H148A/H453A. These results suggest that the histidine residues play a role in transmission of the signal between the catalytic and allosteric sites.
Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
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D000251:Adenosine Triphosphatases / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D053501:Arsenite Transporting ATPases; D001483:Base Sequence; D017124:Conserved Sequence; D017931:DNA Primers / Q000235:genetics; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D006639:Histidine / Q000235:genetics; D006801:Humans; D016623:Ion Pumps; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D014357:Trypsin
D017931:DNA Primers; D016623:Ion Pumps; D009097:Multienzyme Complexes; D006639:Histidine; D014357:Trypsin; D000251:Adenosine Triphosphatases; D053501:Arsenite Transporting ATPases