title: DNA-induced conformational changes in RecA protein. Evidence for structural heterogeneity among nucleoprotein filaments and implications for homologous pairing.
abstract: We have used circular dichroism as a probe to characterize the solution conformational changes in RecA protein upon binding to DNA. This approach revealed that RecA protein acquires significant amounts of alpha-helix upon interaction with DNA. These observations, consistent with the data from crystal structure (Story, R. M., Weber, I., and Steitz, T. (1992) Nature 355, 318-325), support the notion that some basic domains including the DNA binding motifs of RecA protein are unstructured and might contribute to the formation of alpha-helix. A comparison of nucleoprotein filaments comprised of RecA protein and a variety of DNA substrates revealed important structural heterogeneity. The most significant difference was observed with poly(dG). poly(dC) and related polymers, rich in GC sequences, which induced minimal amounts of alpha-helix in RecA protein. The magnitude of induction of alpha-helix in RecA protein, which occurred concomitant with the production of ternary complexes, was 2-fold higher with homologous than heterologous duplex DNA. Most importantly, the stimulation of ATP hydrolysis by high salt coincided with that of the induction of alpha-helix in RecA protein. These conformational differences provide a basis for thinking about the biochemical and structural transitions that RecA protein experiences during the formal steps of presynapsis, recognition, and alignment of homologous sequences.
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore.
authors.forename: K A
authors.initials: KA
authors.lastname: Kumar
authors.forename: S
authors.initials: S
authors.lastname: Mahalakshmi
authors.forename: K
authors.initials: K
authors.lastname: Muniyappa
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D001482:Base Composition; D002942:Circular Dichroism; D004247:DNA / Q000502:physiology*; D004789:Enzyme Activation; D004926:Escherichia coli / Q000378:metabolism; D009698:Nucleoproteins / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D011938:Rec A Recombinases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D009698:Nucleoproteins; D004247:DNA; D011938:Rec A Recombinases; D000251:Adenosine Triphosphatases