Western Blotting for Staphylococcus aureus AgrA

Abstract

Staphylococcus aureus has a quorum sensing system to regulate the expression of various virulence factors, which is exerted by the agr locus that encodes agrBDCA and a regulatory RNA called RNAIII. AgrB, AgrD, and AgrC proteins are involved in producing and recognizing extracellular quorum sensing molecules and transduce the signal by altering the phosphorylation status of AgrA, which is a positive transcription factor, to regulate cytolysin genes as well as the RNAIII gene. RNAIII regulates the expression of various virulence genes. Expression of the agr locus has been examined in depth at the transcriptional level, but investigations of translational expression are limited, because immunoglobulin G used to detect a specific protein highly reacts to S. aureus protein A. Here, we report a method to detect AgrA that is the transcription factor encoded by the agr regulatory system. Although this is a specific protocol for western blotting of S. aureus AgrA protein, it can also be used for other S. aureus proteins by using the appropriate antibody.