Figure 5. Characterization of the protease-resistant domains from membrane or EM-associated SecA.

(A) The effect of nucelotide binding on the stability of the M48 domain was determined using similar proteolysis reaction conditions to those undertaken in Fig. 4, except in the presence of 2 mM ATP or AMP-PNP and 4 mM Mg(OAc)₂. (B) The stabilization effect of membranes and N39 with EM on the M48 domain was assayed using proteolytic reactions to those carried out in panel A at the trypsin concentrations indicated. (C) The effect that integrity of the membrane has upon stability of the M48 domain was ascertained by undertaking proteolysis at different concentration of trypsin in the presence of Triton-X100 (1%) or malto-dodecylmaltoside (DM, 2%) as indicated. Reaction conditions used were similar to those defined in panel A.