Diversity of two-component systems: insights into the signal transduction mechanism by the Staphylococcus aureus two-component system GraSR

Abstract

The response to cationic antimicrobial peptides (CAMPs) in Staphylococcus aureus relies on a two-component system (TCS), GraSR, an auxiliary protein GraX and an ATP-binding cassette (ABC) transporter, VraF/G. To understand the signal transduction mechanism by GraSR, we investigated the kinase activity of the cytoplasmic domain of histidine kinase GraS and the interaction with its cognate response regulator GraR. We also investigated interactions among the auxiliary protein GraX, GraS/R and the ATPase protein of the ABC transporter, VraF. We found that GraS lacks autophosphorylation activity, unlike a similar histidine kinase, BceS, of Bacillus subtilis. In addition, the interaction between GraS and GraR is very weak in comparison to the stronger interaction observed between BceS and its conjugated response regulator, BceR, suggesting that CAMP signaling may not flow directly from GraS to GraR. We found that the auxiliary protein GraX interacts with VraF and GraR, and requires the histidine phosphotransfer and dimerization domain of GraS to interact with this protein. Further, VraF requires the GraS region that connects the membrane-bound domain with the cytoplasmic domain of this protein for interaction with GraS. The interactions of GraX with GraS/R and VraF indicate that GraX may serve as a scaffold to bring these proteins in close proximity to GraS, plausibly to facilitate activation of GraS to ultimately transduce the signal to GraR.

Non‐canonical activation of histidine kinase KdpD by phosphotransferase protein PtsN through interaction with the transmitter domain

“…Accessory proteins that stimulate histidine kinase autophosphorylation are often transmembrane proteins, which interact with kinase domains facing the membrane or the periplasm (Gerken & Misra, 2010;Eguchi et al, 2012). A few cytoplasmic proteins that activate TCSs are known, including GraX in S. aureus and UspC in E. coli, which act through scaffolding of cognate kinase-response regulator complexes (Heermann et al, 2009b;Falord et al, 2012;Muzamal et al, 2014). It remains to be investigated, whether PtsN is just the tip on an iceberg of similarly acting accessory proteins that interact directly with the kinase DHp domain and can be easily recruited to regulate additional kinases either positively or negatively.…”

Two Component Regulatory Systems and Antibiotic Resistance in Gram-Negative Pathogens

“…Interestingly, more and more reports have emerged suggesting that TCS–TCS direct interaction may also affect signaling states and act as signal transducers for interacting proteins [116,117,118,119,120]. A clear correlation between structural properties, domain interaction, and signaling states is suggested.…”

Flotillin scaffold activity contributes to type VII secretion system assembly in Staphylococcus aureus

“…For instance, the scaffold UspC regulates the K + uptake signaling cascade in Escherichia coli [ 6 ], and GraX is a scaffold that participates in a signaling transduction cascade in response to antibiotics in the Gram-positive bacterium S . aureus [ 7 , 8 ].…”