FIG. 2.

SacY protein is present in two forms in vivo. (A) B. subtilis cells containing the sacY gene cloned under Pspac promoter control on plasmid pMI3 were induced for SacY production by adding IPTG. The cellular proteins were extracted, after being labeled with [³⁵S]methionine, and analyzed by 2-D gel electrophoresis (isoelectric focusing in one dimension and SDS-PAGE in the second dimension), followed by autoradiography. The insert (top, right) shows fractionation of the same proteins, which were immunoprecipitated with anti-SacY antibodies prior to the 2-D gel analysis. (B) The same cells as described for panel A except that IPTG was not added to the cells. Arrows indicate the positions of the two forms of SacY. Molecular masses of protein standards are given in kilodaltons.