Required for the first step of histidine biosynthesis. May allow the feedback regulation of ATP phosphoribosyltransferase activity by histidine. Amino-acid biosynthesis; L-histidine biosynthesis; L-histidine from 5-phospho-alpha-D-ribose 1-diphosphate: step 1/9. Heterooctamer composed of four HisG and four HisZ subunits. This function is generally fulfilled by the C-terminal part of HisG, which is missing in some bacteria such as this one. The stability and homogeneity of the HisG-HisZ complex is apparently increased by ATP and 5-phosphoribose 1-diphosphate but decreased in the presence of the regulatory inhibitor histidine. Belongs to the class-II aminoacyl-tRNA synthetase family. HisZ subfamily.