FIG. 3.
SpaD pilins are independently synthesized and assembled. C. diphtheriae strain NCTC12139 or its isogenic derivatives carrying deletion of spa genes were treated with muramidase (M) or formic acid (F) or were left untreated (−) prior to extraction with hot SDS sample buffer. Proteins were separated on SDS-PAGE and detected by immunoblotting with the specific antisera α-SpaD (A), α-SpaA (B), α-SpaB (C), and α-SpaC (D). The precursor (e.g., SpaP) and high-molecular-weight mature products (e.g., SpaHMW) of pilus assembly, the position of molecular mass markers, and the stacking gel portion of SDS-PAGE (stack) are indicated. wt, wild type.