Enhanced recA protein binding to Z DNA represents a kinetic perturbation of a general duplex DNA binding pathway.
recA protein binding to duplex DNA is enhanced when a B form DNA substrate is replaced with a left-handed Z form helix. This represents a kinetic rather than an equilibrium effect. Binding to Z DNA is much faster than binding to B DNA. In other respects, binding to the two DNA forms is quite similar. recA protein binds to B or Z DNA with a stoichiometry of 1 monomer/4 base pairs. The final protein filament exhibits a right-handed helical structure when either B or Z form DNAs are bound. There are only two evident differences: the kcat for ATP hydrolysis is reduced 3-4-fold when Z DNA is bound, and recA binding at equilibrium is less stable on Z DNA than on B DNA. At steady state, the binding favors B DNA in competition experiments. The results indicate that Z DNA binding by recA protein follows the same pathway as for recA binding to B DNA, but that the nucleation step is faster on the Z form helix.
Kim
J I
JI
Department of Biochemistry, University of Wisconsin, Madison 53706.
Heuser
J
J
Cox
M M
MM
D004247:DNA / Q000378:metabolism* / Q000648:ultrastructure; D004926:Escherichia coli / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008854:Microscopy, Electron; D009690:Nucleic Acid Conformation; D011089:Polydeoxyribonucleotides / Q000378:metabolism*; D011485:Protein Binding; D011938:Rec A Recombinases / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D012261:Ribonucleoproteins / Q000648:ultrastructure; D013329:Structure-Activity Relationship
D011089:Polydeoxyribonucleotides; D012261:Ribonucleoproteins; D004247:DNA; D011938:Rec A Recombinases