| Primary Identifier | IPR004517 | Type | Family |
| Short Name | HisZ |
| description | Protein in this entry are mostly annotated as the ATP phosphoribosyltransferase regulatory subunit (HisZ). However, this entry also includes some histidine-tRNA ligases (HisS or HisRS), which is the paralogue of HisZ. Despite the significant sequential and structural similarity, HisRS and HisZ have different functions []. HisRS is a class IIa aminoacyl-tRNA synthetase (ligase), while HisZ is a regulatory subunit of the hetero-octameric ATP phosphoribosyl transferase that regulate reactions initiating histidine biosynthesis [, ]. From the phylogenetic analysis, HisZ proteins form a monophyletic group that attaches outside the predominant bacterial HisRS clade []. HisZ are represented in a highly divergent set of bacteria (including an aquificale, cyanobacteria, firmicutes, and proteobacteria), but are missing from other bacteria, including mycrobacteria and certain proteobacteria []. It has been suggested that the absences of HisZ from bacteria are due to its loss during evolution []. |
