Influence of the presence of the signal sequence on YedY DMSO reductase activity in R. sphaeroides. Non-denaturing PAGE of soluble extracts (25 μg) from R. sphaeroides f. sp. denitrificans, stained with dithionite-reduced benzyl viologen and DMSO as substrate. Lane WT: wild-type harboring an empty plasmid. Lane -SS: wild-type harboring the pSM181 plasmid (which contains only the sequence encoding the mature protein with an N-terminal 6 His-tag). Lane + SS: wild-type harboring the plasmid pSM196 (which contains the signal sequence upstream of the sequence encoding the mature protein). Pictures were taken at two different times after addition of substrate. The arrows indicate the bands that correspond to the DMSO reductase DmsA, the chromosome-encoded YedY, and the plasmid-encoded His-tagged YedY.