The σ E Cell Envelope Stress Response of Streptomyces coelicolor Is Influenced by a Novel Lipoprotein, CseA

Abstract

We have investigated the role of CseA in the σ ^E cell envelope stress response of the gram-positive bacterium Streptomyces coelicolor . σ ^E is an extracytoplasmic function RNA polymerase sigma factor required for normal cell envelope integrity in S. coelicolor . σ ^E is encoded within a four-gene operon that also encodes CseA, a protein of unknown function, CseB, a response regulator and CseC, a transmembrane sensor histidine kinase (Cse represents c ontrol of s igma E ). Previous work has shown that transcription of the sigE gene is completely dependent on the CseBC two-component system and that the CseBC-σ ^E signal transduction system is induced by a wide variety of cell-wall-damaging agents. Here we address the role of CseA, a protein with no homologues outside the streptomycetes. We show that CseA is a novel lipoprotein localized to the extracytoplasmic face of the cell membrane and that loss of CseA results in upregulation of the sigE promoter.