AP Biology Quiz
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CELL COMMUNICATION AND CELL CYCLE
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A bacterial two-component system uses membrane sensor kinase S and response regulator R. Ligand L binds S, triggering autophosphorylation on histidine and transfer of the phosphate to aspartate on R. Phosphorylated R binds enzyme E and increases its catalytic rate. S also has phosphatase activity that dephosphorylates R when L is absent. A mutant S lacks phosphatase activity but retains kinase activity. After brief L exposure, phosphorylated R remains high longer in the mutant than in wild type. Which outcome is most likely in the mutant after L removal?
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