Effect of HupF on HupL stability under high oxygen tensions. Time course of immunodetection of HupL (panel A) and HypB (panel B) proteins in cell crude extracts from cultures previously induced for hydrogenase activity and then bubbled with 1% O2 or air (21% O2) for the indicated periods of time (min). Top, medium, and bottom panels correspond to cell extracts from R. leguminosarum UPM1155 derivative strains harboring plasmids pALPF1 (wt), pALPF5 (ΔhupF), and pALPF14 (ΔhypC), respectively. Conditions of SDS-PAGE and loading are as in Figure 2. Lanes labelled as 0 contain control crude extracts harboring either unprocessed HupL from UPM1155(pALPF14) (ΔhypC), in top panel, or processed HupL from UPM1155(pALPF14) (wt), in medium and bottom panels as controls. Marks on the left margins indicate the position of the unprocessed (u, 66 kDa) and processed (p, 65 kDa) forms of HupL in panel A, and marks on the right margins indicate the position of molecular weight markers.