D-ribose metabolism in Escherichia coli K-12: Genetics, regulation, and transport

We have isolated mutants defective in high-affinity D-ribose transport. The mutations map in rbsT or rbsB, the structural gene for ribose binding protein. rbsT consists of at least one gene coding for a protein required for high-affinity transport. The high-affinity transport-defective mutants were able to utilize D-ribose, indicating that at least a second, low-affinity transport system for D-ribose is present in Escherichia coli K-12, rbsT and rbsB are located at min 84 on the E. coli genetic map and, together with rbsK, the gene coding for ribokinase, constitute an rbs operon. The order of genes is rbsP/O rbsT ribsB rbsK. The rbs operon is subject to negative control by the product of the rbsR gene, rbsR gene is located distal to the rbs operon and appears to form a separate transcriptional unit.