Q. Wang et Jm. Calvo, LRP, A MAJOR REGULATORY PROTEIN IN ESCHERICHIA-COLI, BENDS DNA AND CAN ORGANIZE THE ASSEMBLY OF A HIGHER-ORDER NUCLEOPROTEIN STRUCTURE, EMBO journal, 12(6), 1993, pp. 2495-2501
Lrp (Leucine-responsive regulatory protein) is a global regulatory pro
tein that controls the expression of many operons in Escherichia coli.
One of those operons, ilvIH, contains six Lrp binding sites located w
ithin a several hundred base pair region upstream of the promoter regi
on. Analysis of the binding of Lrp to a set of circularly permuted DNA
fragments from this region indicates that Lrp induces DNA bending. Th
e results of DNase I footprinting experiments suggest that Lrp binding
to this region facilitates the formation of a higher-order nucleoprot
ein structure. To define more precisely the degree of bending associat
ed with Lrp binding, one or two binding sites were separately cloned i
nto a pBend vector and analyzed. Lrp induced a bend of approximately 5
2-degrees upon binding to a single binding site, and the angle of bend
ing is increased to at least 135-degrees when Lrp binds to two adjacen
t sites. Lrp-induced DNA bending, and a natural sequence-directed bend
that exists within ilvIH DNA, may be architectural elements that faci
litate the assembly of a nucleoprotein complex.