FIG. 4.

H. volcanii PibD processes class III signal peptide-containing preproteins, including flagellins and other pilin-like proteins. (A) H. volcanii H98 (wt) and MT3 (ΔpibD) strains expressing FlgA1/FlgA2-His were grown to mid-log phase in CA medium in which the promoter was turned on and off by the addition of tryptophan. (B) H. volcanii H98 (wt) and MT3 (ΔpibD) strains expressing FlgA1/FlgA2-His, Hvo_A0632-His, or Hvo_02451-His in a tryptophan-inducible manner were grown to mid-log phase in CX plus tryptophan. Equivalent amounts of whole-cell lysates were subjected to SDS-PAGE and visualized by immunoblotting using an anti-His antibody. Cell extracts of H98 (wt) and ΔpibD strains expressing C-terminally His-tagged Hvo_A0632 were also tested for S-layer (cell-wall) glycoprotein (CWG) migration by immunoblotting using an anti-CWG antibody (23). Predicted positions of precursor (p) and mature (m) proteins are indicated. The lower bands in the Hvo_2451 lanes, indicated by an asterisk, are likely degradation products of Hvo_2451 precursor and mature proteins. The migration of molecular mass standards (expressed in kilodaltons) is indicated on the right.