Interactions between the Cytoplasmic Domains of PspB and PspC Silence the Yersinia enterocolitica Phage Shock Protein Response

• Published in: Journal of bacteriology 2016-12, Vol.198 (24), p.3367-3378
• Main Authors: Flores-Kim, Josué, Darwin, Andrew J
• Format: Article
• Language: English
• Subjects: Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Cytoplasm; Gene Expression Regulation, Bacterial; Gene Silencing; Gram-negative bacteria; Mutation; Protein Binding; Protein Domains; Proteins; Spotlight; Stress response; Yersinia enterocolitica - chemistry; Yersinia enterocolitica - genetics; Yersinia enterocolitica - metabolism
• ISSN: 0021-9193; 1098-5530
• DOI: 10.1128/JB.00655-16

The phage shock protein (Psp) system is a widely conserved cell envelope stress response that is essential for the virulence of some bacteria, including Yersinia enterocolitica Recruitment of PspA by the inner membrane PspB-PspC complex characterizes the activated state of this response. The PspB-PspC complex has been proposed to be a stress-responsive switch, changing from an OFF to an ON state in response to an inducing stimulus. In the OFF state, PspA cannot access its binding site in the C-terminal cytoplasmic domain of PspC (PspC ), because this site is bound to PspB. PspC has another cytoplasmic domain at its N-terminal end (PspC ), which has been thought to play a role in maintaining the OFF state, because its removal causes constitutive activation. However, until now, this role has proved recalcitrant to experimental investigation. Here, we developed a combination of approaches to investigate the role of PspC in Y. enterocolitica Pulldown assays provided evidence that PspC mediates the interaction of PspC with the C-terminal cytoplasmic domain of PspB (PspB ) in vitro Furthermore, site-specific oxidative cross-linking suggested that a PspC -PspB interaction occurs only under noninducing conditions in vivo Additional experiments indicated that mutations in pspC might cause constitutive activation by compromising this PspC binding site or by causing a conformational disturbance that repositions PspC in vivo These findings have provided the first insight into the regulatory function of the N-terminal cytoplasmic domain of PspC, revealing that its ability to participate in an inhibitory complex is essential to silencing the Psp response. The phage shock protein (Psp) response has generated widespread interest because it is linked to important phenotypes, including antibiotic resistance, biofilm formation, and virulence in a diverse group of bacteria. Therefore, achieving a comprehensive understanding of how this response is controlled at the molecular level has obvious significance. An integral inner membrane protein complex is believed to be a critical regulatory component that acts as a stress-responsive switch, but some essential characteristics of the switch states are poorly understood. This study provides an important advance by uncovering a new protein interaction domain within this membrane protein complex that is essential to silencing the Psp response in the absence of an inducing stimulus.