Intrinsic negative feedback governs activation surge in two-component regulatory systems.
PhoP and PhoQ comprise a two-component system in the bacterium Salmonella enterica. PhoQ is the sensor kinase/phosphatase that modifies the phosphorylation state of the regulator PhoP in response to stimuli. The amount of phosphorylated PhoP surges after activation, then declines to reach a steady-state level. We now recapitulate this surge in vitro by incubating PhoP and PhoQ with ATP and ADP. Mathematical modeling identified PhoQ's affinity for ADP as the key parameter dictating phosphorylated PhoP levels, as ADP promotes PhoQ's phosphatase activity toward phosphorylated PhoP. The lid covering the nucleotide-binding pocket of PhoQ governs the kinase to phosphatase switch because a lid mutation that decreased ADP binding compromised PhoQ's phosphatase activity in vitro and resulted in sustained expression of PhoP-dependent mRNAs in vivo. This feedback mechanism may curtail futile ATP consumption because ADP not only stimulates PhoQ's phosphatase activity but also inhibits ATP binding necessary for the kinase reaction.
Section of Microbial Pathogenesis, Yale School of Medicine, 295 Congress Avenue, 354D, New Haven, CT 06536, USA.
Won-Sik
WS
Yeo
Igor
I
Zwir
Henry V
HV
Huang
Dongwoo
D
Shin
Akinori
A
Kato
Eduardo A
EA
Groisman
D000255:Adenosine Triphosphate / Q000737:chemistry; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D001665:Binding Sites; D003198:Computer Simulation; D025461:Feedback, Physiological; D007700:Kinetics; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012486:Salmonella typhimurium / Q000201:enzymology*; D015398:Signal Transduction; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics
D001426:Bacterial Proteins; C079792:PhoQ protein, Bacteria; C409039:PmrB protein, bacteria; D014157:Transcription Factors; C081902:pmrA protein, Bacteria; C061064:PhoP protein, Bacteria; D000255:Adenosine Triphosphate