In vivo and in vitro synthesis of the spore-specific proteins A and C of bacillus megaterium

Abstract

Pulse labeling of cells of Bacillus megaterium followed by cell disruption and immunoprecipitation has shown that the spore-specific Proteins A and C are synthetized only during a discrete time period in sporulation. At its maximum, the synthesis of the A- and C-proteins accounted for 5% of the protein being synthesized in vivo, but the mRNA for the A- and C-proteins had a lifetime no longer than that of other mRNAs translated at that time. No evidence was found for synthesis of Proteins A or C in high molecular weight precursor form, and essentially all of the newly synthesized A- and C-protein was found in the forespore. Isolation of total RNA from cells in various stages of growth and sporulation, translation of this RNA in a cell-free system from vegetative cells, and immunoprecipitation showed that the ability of cellular RNA to promote A- and C-protein synthesis in vitro was directly proportional to the rate at which the cells had been synthesizing Proteins A and C in vivo. These data indicate that synthesis of Proteins A and C during sporulation in B. megaterium is primarily under transcriptional control. The identity of the immunoprecipitated labeled material material synthesized in vitro with the A- and C-proteins was established by: 1) their co-migration on sodium dodecyl sulfate-polyacrylamide gels; 2) co-migration on high performance liquid chromatography of tryptic peptides from an [35S]methionine-labeled immunoprecipitate with the methionine-containing tryptic peptides of the A- and C-proteins; and 3) digestion of the labeled immunoprecipitate with a protease specific for the A- and C-proteins.