TABLE 2.

DNA unwinding rates and kinetic parameters for WT and mutant RecBCD

All parameters except RecBC were determined in buffer M₂₅₀ plus 10 mm Mg²⁺, 5 mm ATP, and 7.5 mg/ml heparin. Reaction time courses were fit to Scheme 1 using non-linear least square methods as described previously (22). DNA unwinding rates were calculated by k_U timing step size m. Standard deviations are calculated based on three or four observations.

Enzyme	DNA unwinding rate	Step size m	kU	kNP
	bp/s	bp	s−1	s−1
RecBCa	320 ± 7	3.5 ± 0.1	92 ± 12	1.9 ± 0.6
RecBCD	539 ± 27	3.1 ± 0.7	175 ± 40	4.0 ± 1.7
RecBK29QCD	161 ± 36	3.2 ± 0.8	51 ± 12	2.2 ± 0.6
RecBY803HCD	212 ± 36	5.3 ± 1.7	43 ± 8	2.3 ± 1.4
RecBCDK177Q	391 ± 34	4.3 ± 0.5	90 ± 4	4.7 ± 1.6
RecBCDY567H	452 ± 31	4.5 ± 1.3	106 ± 26	2.2 ± 1.0

^a The DNA unwinding rate of RecBC was determined in buffer M₃₀ plus 10 mm Mg²⁺ and 5 mm ATP (22).