The hisB gene, found in the
enterobacteria (such as ''
E. coli
''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escher ...
''), in ''
Campylobacter jejuni'' and in ''
Xylella
''Xylella fastidiosa'' is an aerobic, Gram-negative bacterium, Gram-negative bacterium of the genus ''Xylella''. It is a plant pathogen, that grows in the water transport tissues of plants (Xylem, xylem vessels) and is transmitted exclusively by ...
''/''
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
The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide, referring to the free amine group (-NH2) located at the end of a polypeptide. Within a peptide, the ami ...
, 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.
Reactions
hisB-N
:D-erythro-1-(imidazol-4-yl)glycerol 3-phosphate
3-(imidazol-4-yl)-2-oxopropyl phosphate + H
2O
hisB-C
:L-histidinol phosphate + H
2O
L-histidinol + phosphate
Non-fusion protein in other species
HIS3 from ''Saccharomyces cerevisiae'' is not a fused IGP dehydratase and hisidinol phosphatase, but an IGPD only (homologous to hisB-N). Whereas HIS2 is the HP (analogous to hisB-C, called hisJ in some prokaryotes).
References
Genes
{{gene-stub