AN ESCHERICHIA-COLI CURVED DNA-BINDING PROTEIN WHOSE EXPRESSION IS AFFECTED BY THE STATIONARY-PHASE SPECIFIC SIGMA-FACTOR SIGMA(S)

From Escherichia coli, a DNA-binding protein that preferentially recognizes a curved DNA sequence was isolated and shown to correspond to one that has recently been reported as a binding protein for the replication origin of the E. coli chromosome, named Rob. Here, a rob promoter-lacZ transcriptional fusion was constructed on the chromosome, and used to demonstrate that the expression of rob is notably enhanced at the onset of stationary phase in Luria-broth and also under certain growth conditions in a minimal medium, such as glucose- and phosphate-starvation medium. It was further shown that this growth condition-dependent expression of rob is notably reduced in a null mutant for the stationary phase-specific sigma subunit of RNA polymerase, sigma(s), although sigma(s)-independent expression of rob was significant during the logarithmic growth phase. Furthermore the rob null mutant was found to exhibit, as compared with the wild-type, an altered profile of protein synthesis, particularly at the very late stationary phase.