Fig. 2. Subunit composition of the SecYEG complex. (A) Immuno precipitation using SecY or SecG antibodies. A 5 µl aliquot (10%) of the total bound material was applied directly to the gel. Lanes 1 and 2 denote the material precipitated by SecY and SecG antibodies, respectively. Lane 3 is a sample of purified SecYEG for reference. The molecular weight markers are the same as those shown in Figure 1. The positions of SecY, E and G are indicated. (B) SDS–PAGE analysis of the crystalline SecYEG specimen (lane 4).