IMPLICATION OF RbsD OF THE D-RIBOSE HIGH-AFFINITY TRANSPORT SYSTEM OF ESCHERICHIA COLI AS A REGULATOR OF RIBOKINASE ACTIVITY

The D-ribose high-affinity transport operon (RbsDACBKR) of Escherichia coli encodes the proteins necessary for high-affinity transport and utilization of D-ribose. rbsD encodes a 15 kDa protein that is not essential for D-ribose high-affinity transport. RbsD is unique as a component of a highaffinity transport system in that it has a TonB box at its amino terminus. Neither RbsD or RbsK are required for D-ribose high-affinity transport, but their potential interaction with each other has not been examined. Characterization of a rbs operon mutant at the TonB box of RbsD implicates the RbsD gene product as a regulator of ribokinase (RbsK) activity.