Wikipedia
The hisB gene, found in the enterobacteria (such as E. coli), in Campylobacter jejuni and in Xylella/ Xanthomonas encodes a protein involved in catalysis of two step in histidine biosynthesis (the sixth and eight step), namely the bifunctional Imidazoleglycerol-phosphate dehydratase/ histidinol-phosphatase.
The former function , found at the N-terminal, dehydrated d-erythroimidazoleglycerolphosphate to imidazoleacetolphosphate, the latter function , found at the C-terminal, dephosphorylates l-histidinolphosphate producing histidinol.
The firth step is catalysed instead by histadinolphosphate aminotransferase (encoded by hisC)
The peptide is 40.5kDa and associates to form a hexamer (unless truncated)
In E. coli hisB is found on the hisGDCBHAFI operon
The phosphatase activity possess a substrate ambiguity and overexpression of hisB can rescue phosphoserine phosphatase (serB) knockouts.