E. Oriol et al., CLONING OF THE RHODOBACTER-SPHAEROIDES HISI GENE - UNIFUNCTIONALITY OF THE ENCODED PROTEIN AND LACK OF LINKAGE TO OTHER HIS GENES, Microbiology, 142, 1996, pp. 2071-2078
The Rhodobacter sphaeroides 2.4.1 hisl gene, which encodes a phosphori
bosyl-AMP-cyclohydrolase that catalyses the third step in the histidin
e biosynthetic pathway, has been isolated from a genomic library of th
is phototrophic bacterium by complementation of an Escherichia coil hi
sl mutant. Analysis of the nucleotide sequence of the R. sphaeroides h
isl gene reveals that it encodes a deduced product of 119 aa with a pr
edicted molecular mass of 13.4 kDa. In contrast to the situation in E.
coil, the R. sphaeroides hisl gene encodes a unifunctional protein an
d it is not linked to the hisE gene. The absence of a single histidine
operon like that of E. coil was confirmed by PFGE experiments and com
plementation analysis of a R. sphaeroides hisl mutant that was constru
cted by marker exchange. The location of hisl in the R. sphaeroides ge
nome has been determined to be at map co-ordinate 2275+/-20 of chromos
ome I.