Journal Article

Structural Insights Into the Activity of Transcriptional Enhancer-Binding Proteins

Robinson, Carol V, Zhang, Xiaodong, Bordes, Patricia, Keetch, Catherine A, Rappas, Mathieu, Schumacher, Jorg, Niwa, Hajime, Wigneshweraraj, Sivaramesh, Buck, Martin, Beuron, Fabienne

2005

Overview

Activators of bacterial σ54-RNA polymerase holoenzyme are mechanochemical proteins that use ATP hydrolysis to activate transcription. We have determined a 20 Å resolution structure of an activator, PspF(1-275), bound to an ATP transition state analog (ADP.AlFx), in complex with its basal factor σ54 by cryo-electron microscopy. By fitting the crystal structure of apo PspF(1-275) at 1.75 Å into the EM map we identify two loops involved in binding σ54. By comparing enhancer-binding structures in different nucleotide states and mutational analysis, we propose nucleotide dependent conformational changes that free the loops for association with σ54.