Bhattacharjee H, Rosen B P
Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Biometals. 2000 Dec;13(4):281-8. doi: 10.1023/a:1009200215328.
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.
ArsA ATP酶是一种泵的催化亚基，该泵负责大肠杆菌对砷化物和锑化物的抗性。亚砷酸盐或亚锑酸盐通过变构作用激活ArsA ATP酶的活性。来自真细菌、古细菌和真核生物的ArsA同源物具有一个特征序列（DTAPTGHT），其中包含一个保守的组氨酸。ArsA ATP酶有两个这样的保守基序，一个在蛋白质的NH2末端（A1）一半，另一个在COOH末端（A2）一半。这些序列被认为是信号转导结构域，可将变构位点上金属占据的信息传递到催化位点以激活ATP水解。通过诱变产生H148A、H453A或H148A/H453A ArsA，研究了分别位于A1和A2信号转导结构域中的保守残基His148和His453的作用。每种改变后的蛋白质在类金属激活的ATP水解的Vmax方面均表现出下降，顺序为野生型ArsA>H148A>H453A>H148A/H453A。这些结果表明，组氨酸残基在催化位点和变构位点之间的信号传递中起作用。
