Table 2.

Calculated kinetic parameters for wild type SecA in the context of various translocation partners

Condition	KM[ATP], μM	kcat, min−1	kcat, s−1	kcleave, s−1
+Mg2+	0.32 ± 0.03*	0.56 ± 0.01*	0.01 ± 1.7 × 10−4	6.14 ± 0.02†
−Mg2+	50.8 ± 3.2*	22.4 ± 0.28*	0.37 ± 4.6 × 10−3	30.4 ± 0.44
+Mg2+; 1 μM SecYEG in proteoliposomes (* in Fig. 1B)	51.1 ± 7.8	15.9 ± 0.62	0.27 ± 0.01	11.5 ± 0.07
+Mg2+; 1 mM SecYEG in proteoliposomes; 0.75 μM proOmpA (* in Fig. 2B)	46.1 ± 6.6	456.3 ± 17.21	7.6 ± 0.27	17.9 ± 0.15

The steady-state ATPase activity of purified wild type SecA was measured with increasing concentrations of ATP, and fitted according to Eq. 2 in SI Equations to determine values for K_M[ATP] and k_cat. Values for k_cleave were derived from the pre-steady-state ATPase data shown in Figure 5 and are compared with the values for k_cat in seconds. SE from the fitting procedure is shown.

*Data published in ref. 14.

^†This value was determined to be 1.9 s⁻¹ by quenched flow rapid mixing, the difference explained by the inherent inaccuracies of this method.