Adenylate Charge Regulates Sensor Kinase CheS3 To Control Cyst Formation in XXXX .

@entity857 @entity3793 @entity5498 @entity72064 @entity2483 @entity855
@entity72064 forms metabolically dormant cysts under unfavorable growth conditions such as desiccation or nutrient starvation. The development of cysts is tightly regulated and involves a cyst-repressing chemotaxis-like signal transduction pathway called the Che3 signaling cascade. The Che3 cascade is comprised of a @entity5498 chemoreceptor (MCP3), receptor-methylating/demethylating proteins CheB3 and CheR3, two CheW3 linker proteins, a CheA3-CheY hybrid @entity3793 kinase, and a single-domain response regulator, CheY3. In @entity2483 , the Che3 cascade also contains a second hybrid @entity3793 kinase, CheS3. Recent biochemical and genetic studies show that CheA3 does not serve as a phosphor donor for CheY3; instead, CheA3 inhibits a CheS3 > CheY3 two-component system by phosphorylating an inhibitory receiver domain of CheS3. In this study, we show that in addition to phosphorylation by CheA3, the phosphorylation state of CheS3 is also regulated by the cellular energy level as quantified by the molar ratio of @entity855 /( @entity855 + @entity857 ). A 35% decrease in cellular energy is shown to occur in vivo upon a nutrient downshift that gives rise to cyst formation. When this energy decline is replicated in vitro, the phosphorylation level of CheS3 is reduced by ~75%. Finally, we also show that @entity857 -mediated reduction of CheS3 phosphorylation is a consequence of @entity857 enhancing autodephosphorylation of CheS3. IMPORTANCE: Upon starvation, @entity72064 undergoes a developmental process that forms metabolically dormant cysts, which withstand desiccation and nutritional limitation. This study explores the role of the cellular energy state as measured by the ratio of @entity855 to @entity857 as an important regulator of cyst formation in @entity72064 . We show that @entity72064 cells experience a significant reduction in @entity855 during cyst formation using @entity855 /( @entity855 + @entity857 ) as a measurement. When this in vivo level of energy starvation is simulated in vitro, CheS3 phosphorylation is reduced by 75%. This profound reduction in CheS3 autophosphorylation is contrasted with a much lower 25% decrease in CheA3 phosphorylation in response to a similar downward shift in @entity855 /( @entity855 + @entity857 ). We argue that even though adenylate energy affects all @entity855 -dependent enzymes to an extent, the enhanced inhibition of CheS3 activity in response to a reduction in the @entity855 /( @entity855 + @entity857 ) ratio likely functions as an important input signal to regulate cyst development.
