Table 1. Biochemical properties of wild-type and mutant SecA proteins.

SecA variant	KD Ribosomes*	KD VipB†	Basal ATPase activity‡	TM§
Wild type	640 ± 33 nM	0.9 μM	0.053 ± 0.02 s−1	40.7 ± 0.09°C
SecAΔMBD	160 ± 35 nM	1.7 μM	<0.001 s−1	42.0 ± 0.08°C
SecAΔCTT	920 ± 38 nM	5.9 μM	0.91 ± 0.02 s−1	40.0 ± 0.1°C
SecAC885A/C887A	ND¶	>10 μM	<0.001 s−1	ND¶
SecABpa852	ND¶	>10 μM	<0.001 s−1	ND¶

^*Equilibrium dissociation constant of the complex between SecA and non-translating 70S ribosomes as determined by fluorescence anisotropy. Confidence intervals are the standard error of the fit.

^†Equilibrium dissociation constant of the complex between SecA and IAANS-labelled VipB peptide as determined by change in fluorescence.

^‡Rate of ATP hydrolysis by SecA in the absence of substrate protein and SecYEG.

^§Denaturation midpoint temperature as determined by the change in circular dichroism at 222 nm.

^¶not determined.