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Structural Insights into the Activity of Enhancer-Binding Proteins

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Science  25 Mar 2005:
Vol. 307, Issue 5717, pp. 1972-1975
DOI: 10.1126/science.1105932

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Abstract

Activators of bacterial σ54–RNA polymerase holoenzyme are mechanochemical proteins that use adenosine triphosphate (ATP) hydrolysis to activate transcription. We have determined by cryogenic electron microscopy (cryo-EM) a 20 angstrom resolution structure of an activator, phage shock protein F [PspF(1-275)], which is bound to an ATP transition state analog in complex with its basal factor, σ54. By fitting the crystal structure of PspF(1-275) at 1.75 angstroms into the EM map, we identified two loops involved in binding σ54. Comparing enhancer-binding structures in different nucleotide states and mutational analysis led us to propose nucleotide-dependent conformational changes that free the loops for association with σ54.

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