Investigating protein–protein interfaces in bacterial transcription complexes: a fragmentation approach

Transcription initiation by σ 54 –RNA polymerase (RNAP) relies explicitly on a transient interaction with a complex molecular machine belonging to the AAA+ (ATPases associated with various cellular activities) superfamily. Members of the AAA+ superfamily convert chemical energy derived from NTP hydrolysis to a mechanical force used to remodel their target substrate. Recently Bordes and colleagues,1 using a protein fragmentation approach, identified a unique sequence within σ 54 ‐dependent transcriptional activators that constitutes a σ 54 ‐binding interface. This interface is not static, but subject to nucleotide‐dependent movement which may represent a common mechanism for controlling output that has been adopted by other AAA+ proteins. BioEssays 25:1150–1153, 2003. © 2003 Wiley Periodicals, Inc.