Escherichia coli MutL loads DNA helicase II onto DNA.
Previous studies have shown that MutL physically interacts with UvrD (DNA helicase II) (Hall, M. C., Jordan, J. R., and Matson, S. W. (1998) EMBO J. 17, 1535-1541) and dramatically stimulates the unwinding reaction catalyzed by UvrD in the presence and absence of the other protein components of the methyl-directed mismatch repair pathway (Yamaguchi, M., Dao, V., and Modrich, P. (1998) J. Biol. Chem. 273, 9197-9201). The mechanism of this stimulation was investigated using DNA binding assays, single-turnover helicase assays, and unwinding assays involving long duplex DNA substrates. The results indicate that MutL binds DNA and loads UvrD onto the DNA substrate. The interaction between MutL and DNA and that between MutL and UvrD are both important for stimulation of UvrD-catalyzed unwinding. MutL does not clamp UvrD onto the substrate; and therefore, the processivity of unwinding is not increased in the presence of MutL. The implications of these results are discussed, and models are presented for the mechanism of MutL stimulation as well as for the role of MutL as a master coordinator in the methyl-directed mismatch repair pathway.
Mechanic
L E
LE
Departments of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Frankel
B A
BA
Matson
S W
SW
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D020137:Base Pair Mismatch; D001483:Base Sequence; D002384:Catalysis; D004265:DNA Helicases; D004260:DNA Repair; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D000070956:MutL Proteins; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000378:metabolism
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C074770:MutL protein, E coli; D009838:Oligodeoxyribonucleotides; D000251:Adenosine Triphosphatases; C506746:UvrD protein, E coli; D000070956:MutL Proteins; D004265:DNA Helicases