Characterization and comparison of mycobacterial antigens by two-dimensional polyacrylamide gel electrophoresis

Cell extracts and culture filtrates were prepared from several mycobacterial species and subjected to two-dimensional acrylamide gel electrophoresis. The cell preparations were first electrophoresed in a 7% homogeneous gel followed by a second electrophoresis, at right angles to the first separation, in a 2 to 30% linear gel gradient slab. Because the stained slab resembled a "fingerprint" or "peptide map," this procedure has been called "electroprotein mapping." More than 200 protein-staining spots were detected in several of the cell extracts, each map being characteristic of the species examined. The single most characteristic portion of each map was the region between the 16 and 30% gel concentrations. This region consisted of several small-molecular-weight components (many of peptide proportions) which together appeared as the most anodic band in the 7% gel column (first separation). The number and location of these components in the linear gel slab (second separation) were specific for each species tested. By electrophoresis of molecular-weight markers (i.e., albumin, myoglobin, cytochrome c) with and across (transverse electrophoresis) the gel gradient, the relative molecular weights of the unknown cell extract components could be estimated. These results suggest that two-dimensional acrylamide gel electrophoresis is a useful tool for the characterization of mycobacterial cell constituents.