FIG 3.
PenA is a lipoprotein. (A) Inhibition of signal peptidase II with globomycin results in accumulation of PenA prolipoprotein. Whole cells of strain Bp82 ΔpenA::mini-Tn7-Km-Ptac-penA (Ptac-penA) induced with IPTG, with or without treatment with 250 μg/ml globomycin, were analyzed by Western blotting using anti-PenA antibodies. Untreated whole cells of strain Bp82 ΔpenA were included as a control. The positions of bands corresponding to prolipoprotein and lipoprotein are marked. (B) The molecular mass of PenA is consistent with it being a lipoprotein. Mass spectrometric analysis of membrane proteins extracted from strains Bp82 ΔpenA (blue trace) and Bp82 ΔpenA::mini-Tn7-Km-Ptac-penA induced with IPTG (green trace) reveals a peak whose mass is consistent with a triacylated PenA protein.