Two-State Allosteric Behavior in a Single-Domain Signaling Protein

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Science  23 Mar 2001:
Vol. 291, Issue 5512, pp. 2429-2433
DOI: 10.1126/science.291.5512.2429

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Protein actions are usually discussed in terms of static structures, but function requires motion. We find a strong correlation between phosphorylation-driven activation of the signaling protein NtrC and microsecond time-scale backbone dynamics. Using nuclear magnetic resonance relaxation, we characterized the motions of NtrC in three functional states: unphosphorylated (inactive), phosphorylated (active), and a partially active mutant. These dynamics are indicative of exchange between inactive and active conformations. Both states are populated in unphosphorylated NtrC, and phosphorylation shifts the equilibrium toward the active species. These results support a dynamic population shift between two preexisting conformations as the underlying mechanism of activation.

  • * Present address: Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226, USA.

  • To whom correspondence should be addressed. E-mail: dkern{at}

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