Mapping the gene determining ornithine transcarbamylase and its operator in Escherichia coli B

The gene determining ornithine transcarbamylase in Escherichia coli B is argI, not argF. The argI gene has been located at 84 min on the linkage map, close to the gene for aspartate transcarbamylase, with neighboring markers in clockwise order fdp pyrB argI valS. A mutation in its operator locus, argO(I), has been mapped between argI and valS, so that this gene, unlike the argCBH portion of the argECBH cluster, appears to be oriented in the same direction as most of the other known E. coli operons.