Fig. 2.

Refolding of PhoA. (A) Refolding of pre- and ss-PhoA in the presence or absence of SecA. Chemically denatured PhoA was diluted 1:50 in 20 mM Mops, pH 7, containing 0.04% PhoA substrate p-nitrophenyl phosphate and a 2-fold molar excess of SecA or an equal volume of SecA buffer. After refolding for 10 min specific PhoA activity was determined. (B) Refolding of PhoA in the presence of various concentrations of SecA. Refolding was done as described in A except that SecA/PhoA ratios varied as indicated and 10-fold molar excess of BSA was used as a negative control. The added SecA volume was held constant to exclude possible salt effects of the SecA buffer. The refolding factors given represent the enzymatic PhoA activity after refolding in the presence of SecA divided by the PhoA activity after refolding without SecA. Results of samples containing ss-PhoA (Δss) are shown in black and samples containing pre-PhoA (pre), in gray. Bars indicate standard deviation.