Abstract
The Escherichia coli MeIR protein is a transcription activator that autoregulates its own promoter by repressing transcription initiation. Optimal repression requires MeIR binding to a site that overlaps the meIR transcription start point and to upstream sites. In this work, we have investigated the different determinants needed for optimal repression and their spatial requirements. We show that repression requires a complex involving four DNA-bound MeIR molecules, and that the global CRP regulator plays little or no role.