Extra Cytoplasmic Sigma Factors in Staphylococcus aureus; their Role and Significance in the Survival of Cocci

Abstract

Bacterial sigma ($σ$) factors are an essential component of RNA polymerase. It determines the promoter selectivity. Alternative $σ$ factors play key roles in the coordinating gene transcription during various environmental stresses, nutrient starvation responses and during morphological development. The extra cytoplasmic function (ECF) $σ$ factors are small regulatory proteins that are quite divergent in sequence relative to most other $σ$ factors. In many bacteria with complex genome, contain multiple ECF $σ$ factors and these regulators often outnumber all other types of $σ$ factor combined. The roles and mechanisms of regulation for these various ECF $σ$ factors are largely unknown, but significant progress has been made in selected systems like Escherichia coli, Bacillus subtilis, Staphylococcus aureus, and Mycobacterium tuberculosis. Most ECF $σ$ factors are co-transcribed with one or more negative regulators. Upon receiving an appropriate environmental stimulus, the $σ$ factor is released and can bind to RNA polymerase to stimulate transcription. S. aureus causes a variety of human and animal infections. It produces multiple virulence factors as well as different regulators for controlling the expression of virulence factors. Prevention of staphylococcal infections is becoming problematic primarily because of the emergence and dissemination of the multiple-drug-resistant S. aureus strains across the world. Novel anti-staphylococcal drugs are required to eradicate all the S. aureus strains. The depth study of structural characterization of the primary and alternative sigma factors of S. aureus may provide a novel way for the development of anti-staphylococcal drug, as most of them are involved in the regulation of gene expression. The present review studies involve the important aspects ECF $σ$ factors in pathogenesis.