Lrp, a major regulatory protein in Escherichia coli, bends DNA and can organize the assembly of a higher-order nucleoprotein structure.

Abstract

Lrp (Leucine‐responsive regulatory protein) is a global regulatory protein that controls the expression of many operons in Escherichia coli. One of those operons, ilvIH, contains six Lrp binding sites located within a several hundred base pair region upstream of the promoter region. Analysis of the binding of Lrp to a set of circularly permuted DNA fragments from this region indicates that Lrp induces DNA bending. The results of DNase I footprinting experiments suggest that Lrp binding to this region facilitates the formation of a higher‐order nucleoprotein structure. To define more precisely the degree of bending associated with Lrp binding, one or two binding sites were separately cloned into a pBend vector and analyzed. Lrp induced a bend of approximately 52 degrees upon binding to a single binding site, and the angle of bending is increased to at least 135 degrees when Lrp binds to two adjacent sites. Lrp‐induced DNA bending, and a natural sequence‐directed bend that exists within ilvIH DNA, may be architectural elements that facilitate the assembly of a nucleoprotein complex.

Contribution of DNA Conformation and Topology in Right-handed DNA Wrapping by the Bacillus subtilis LrpC Protein

“…However, it seems that LrpC possesses unusual properties among eubacterial DNA structuring proteins, including the Lrp-like family. Whereas E. coli Lrp has been proposed to wrap DNA (35), LrpC, along with the Smj12 protein from Sulfolobus solfataricus (which also overwinds DNA) and the PutR protein from Agrobacterium tumefaciens, are the only members of the Lrplike family for which DNA wrapping has been firmly demonstrated (36,37). Looped structures formed by LrpC where 80 bp of DNA is wrapped resemble eukaryotic dimers of (H 3 -H 4 ) and archaeal HMf or HTz tetrasomes ( Fig.…”

Self-perpetuating epigenetic pili switches in bacteria

“…This mutual binding exclusion effect is reduced from 10-fold to only about 2-fold when unsupercoiled DNAs are used (unpublished data), showing a strong dependence on DNA topology. Because Lrp is known to form higher oligomers under certain conditions (19,20) and bend DNA (21), one possible mechanism is that the conformation of pap sites 4-6 might be altered as a result of a binding of Lrp at sites 1-3 located 102 bp away (measured from site 2 to site 5) (Fig. 1).…”

The leucine-responsive regulatory protein binds to the fim switch to control phase variation of type 1 fimbrial expression in Escherichia coli K-12

“…Therefore, it is likely that the marked stimulation of fim by lrp is either direct or occurs through factors other than FimB and FimE. Lrp, a site-specific DNA-binding protein, controls a regulon of at least 40 genes in Escherichia coli, including fimbrial expression and amino acid transport, degradation, and biosyn-thesis (3,6,9,10,18,19,(22)(23)(24). The most extensive studies of Lrp have examined its role in the regulation of ilvIH transcription (19,22,23). Lrp binds to the promoter region of ilvIH with a high degree of cooperativity, bending the DNA to form a nucleoprotein complex (22,23).…”