. 1999 Aug 3;96(16):8985–8990. doi: 10.1073/pnas.96.16.8985

Table 1.

Covariation between the presence of HisZ and the length of HisG polypeptides in various bacterial species

Organisms	Polypeptide length, no. residues								HisZ homolog
Organisms	HisA	HisB	HisC	HisD	HisF	HisG	HisH	HisIE	HisZ homolog
E. coli	245	356^*	356	434	258	299	196	204	−
H. influenzae	249	362^*	367	427	258	303	199	221	−
S. typhimurium	246	355^*	359	433	258	299	194	203	−
S. solfataricus	232	193	376	398	251	290	199	85	−
M. janischii	237	197	373	429	272	288	198	222	−
L. lactis	240	200	360	430	244	208	202	212	+
Synechocystis sp.	256	161	352	409	261	210	210	230	+
B. subtilis	238	192	354	426	253	214	212	212	+
A. aeolicus	238	192	354	426	253	205	207	205	+

Data are from ref. 35.

In these organisms, the hisB gene encodes a bifunctional enzyme possessing imidazole glycerolphosphate dehydratase and histidinolphosphate phosphatase activities that catalyzes both the sixth and eighth steps of histidine biosynthesis (36).