A global view of Escherichia coli Rsd protein and its interactions

Abstract

The Escherichia coli Rsd protein forms 1 : 1 complexes with σ⁷⁰protein, which is the major factor in determining promoter recognition by RNA polymerase. Here we describe measurements of the levels of Rsd, RNA polymerase, σ⁷⁰ and the alternative σ³⁸ factor. Rsd levels are sufficient to sequester a significant proportion of σ⁷⁰ and immunoaffinity pull-down experiments show that this occurs in stationary phase but not in exponentially growing cells. Rsd expression is controlled by two promoters, P1 and P2. Experiments with lac fusions show that the P2 promoter is stronger than P1, that P2 is active in all phases of growth, and that this accounts for the high levels of Rsd.