Two-state allosteric behavior in a single-domain signaling protein.
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.
National Magnetic Resonance Facility at Madison (NMRFAM), Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA.
B F
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Volkman
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Lipson
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Wemmer
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D
Kern
D000494:Allosteric Regulation; D001426:Bacterial Proteins; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D009038:Motion; D009154:Mutation; D019906:Nuclear Magnetic Resonance, Biomolecular; D051922:PII Nitrogen Regulatory Proteins; D010766:Phosphorylation; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D013995:Time; D015534:Trans-Activators; D014157:Transcription Factors
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D051922:PII Nitrogen Regulatory Proteins; D015534:Trans-Activators; D014157:Transcription Factors