Figure 5.

Leader peptide is not required for binding of nascent polypeptides to SecB. Separate mixtures, programmed with mRNA for p370 (lane p) and m280 (lane m), were combined after translation (lane S) and His₆SecB (0.5 μM) was added. Column chromatography was carried out as described for Fig. 3, except that the volume of the wash was 4 ml. Fractions were analyzed by SDS/PAGE. The intensity profiles of the radioactivity in the lanes S (sample, total applied), F (free, not retained by the His₆SecB on the column), and B (bound, retained on the column and eluted by 0.5 M imidazole), were generated using imagequant software version 4.2 (Molecular Dynamics). The arrow indicates the position for polypeptides of a molecular weight of 23,000, as calculated using the molecular weight markers shown.