Shedding of lipoprotein precursors by diacylglyceryl transferase mutant cells of B. subtilis. To investigate in which form the lipoprotein OpuAC is released into the growth medium of lgtmutant cells, Western blotting experiments were performed with cellular and growth medium fractions of B. subtilis Δlgt, and the control strains 168 and Δlsp. Furthermore, the PrsA and QoxA proteins were used as control lipoproteins. Cells were grown in L-broth at 37°C. Approximately 1 h after entry into the stationary phase, cells were separated from the growth medium by centrifugation. Next, extracellular proteins were concentrated by TCA precipitation. Equivalent amounts of cell and medium fractions were used for SDS-PAGE, Western blotting and immunodetection with antibodies specific for PrsA (A), OpuAC (B), or QoxA (C). Unmodified lipoprotein precursors (white triangles), lipid-modified lipoprotein precursors (white squares), mature lipoproteins (white circles), alternatively processed mature-like lipoproteins (black squares), and degradation products of lipoproteins (black stars) are indicated.
