title: Activation of human meiosis-specific recombinase Dmc1 by Ca2+.
abstract: Rad51 and its meiotic homolog Dmc1 are key proteins of homologous recombination in eukaryotes. These proteins form nucleoprotein complexes on single-stranded DNA that promote a search for homology and that perform DNA strand exchange, the two essential steps of genetic recombination. Previously, we demonstrated that Ca2+ greatly stimulates the DNA strand exchange activity of human (h) Rad51 protein (Bugreev, D. V., and Mazin, A. V. (2004) Proc. Natl. Acad. Sci. U. S. A. 101, 9988-9993). Here, we show that the DNA strand exchange activity of hDmc1 protein is also stimulated by Ca2+. However, the mechanism of stimulation of hDmc1 protein appears to be different from that of hRad51 protein. In the case of hRad51 protein, Ca2+ acts primarily by inhibiting its ATPase activity, thereby preventing self-conversion into an inactive ADP-bound complex. In contrast, we demonstrate that hDmc1 protein does not self-convert into a stable ADP-bound complex. The results indicate that activation of hDmc1 is mediated through conformational changes induced by free Ca2+ ion binding to a protein site that is distinct from the Mg2+.ATP-binding center. These conformational changes are manifested by formation of more stable filamentous hDmc1.single-stranded DNA complexes. Our results demonstrate a universal role of Ca2+ in stimulation of mammalian DNA strand exchange proteins and reveal diversity in the mechanisms of this stimulation.
authors.affiliation: Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, USA.
authors.forename: Dmitry V
authors.initials: DV
authors.lastname: Bugreev
authors.forename: Efim I
authors.initials: EI
authors.lastname: Golub
authors.forename: Alicja Z
authors.initials: AZ
authors.lastname: Stasiak
authors.forename: Andrzej
authors.initials: A
authors.lastname: Stasiak
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Mazin
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000378:metabolism*; D003434:Crossing Over, Genetic; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D008274:Magnesium / Q000494:pharmacology; D008540:Meiosis; D011487:Protein Conformation / Q000187:drug effects; D051135:Rad51 Recombinase; D045522:Recombinases; D011995:Recombination, Genetic
chemical_list: D018797:Cell Cycle Proteins; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D045522:Recombinases; D000255:Adenosine Triphosphate; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; D000251:Adenosine Triphosphatases; C074556:DMC1 protein, human; D008274:Magnesium; D002118:Calcium