B. Excess of SecB inhibits the proOmpA-stimulated translocation ATPase activity of SecA(noCtail). ATPase measured as in Fig. 1C; SecB concentration range: 0-6 µM. Values were normalized (effectmax=100%; effectmin=0%) and plotted (n= 3 biological replicates; mean values ± SEM) versus the log10[SecB4]. The Ki was determined as in Fig. 1E. 