FIG. 2.

Radiosequencing of the protease-resistant SecA fragments. After translocation and proteolysis as described in Materials and Methods, SecA fragments recovered from both membrane pellet (A) and supernatant (B) fractions were separated by SDS-PAGE, transferred to PVDF membrane sheets, and visualized by Coomassie blue staining or immunodetection. Individual bands were then excised from the PVDF membrane sheets and subjected to radiosequencing as described in Materials and Methods. The radiosequencing profiles for each fragment are aligned with the identified sequences. The cleavage sites of trypsin are indicated by arrows. The sequences identified were unique. There is no other match in the SecA sequence except for the 29-kDa fragments, for which all possible sequences are shown.