Suppression of the lethality caused by an overproduced component of ribose transporter

Abstract

The high-affinity uptake of D-ribose in Esherichia coli K-12 requires the RbsACBK proteins encoded by a single rbs operon. Until now, the function of RbsD produced from the same operon is unknown. When we overproduced RbsD in the presence of RbsACBK, this high copy RbsD caused an increase in the rate of D-ribose uptake into the cytoplasm, leading to a cell death. The lethality depends on the presence of RbsK, indicating that the phosphorylation of ribose is responsible for the phenotype. We have isolated fifteen mutations that alleviate the lethality. Nine of them are found in rbsC. Two other mutations, showing a similar phenotype, are in rbsA, and two others in rbsB. The mutations are leaky and reduced the rate of ribose uptake. The current hypothesis is that the lethality caused by a metabolic overflow as a result of RbsD overproduction is alleviated by a reduction in ribose uptake caused by a mutation in the Rbs transporter.