Sugar-coating Acinetobacter baumannii virulence

Transcription factor sliding in live bacteriaThe facilitated diffusion theory has been used to describe how transcription factors combine three-dimensional diffusion in the cytoplasm with one-dimensional sliding on the DNA to locate their specific chromosomal binding sites.The physiological relevance of this phenomenon was recently interrogated in live Escherichia coli cells using a single-molecule imaging assay that examined the binding of a fluorescent LacI repressor to its target operator sequence.In agreement with theoretical predictions, the repressor required 3-5 minutes to bind the operator.The authors went on to directly examine the DNA-sliding mechanism and found that LacI traverses a distance of 45 ± 10 base pairs and that other DNA-binding proteins in close proximity to the operator can impede this sliding process.Moreover, because LacI was frequently observed to slide over the operator, the authors propose that immediate binding of transcription factors at specific sites is probably constrained by the demand to rapidly diffuse along nonspecific sequences in search of these sites.