Purification and characterization of additional low-molecular-weight basic proteins degraded during germination of Bacillus megaterium spores

Abstract

Dormant spores Bacillus megaterium contained a group of low-molecular-weight (5,000 to 11,000) basic (pI greater than 9.4) proteins (termed D, E, F, and G proteins) which could be extracted from disrupted spores with strong acids. These proteins were distinct from the previously described A, B, and C proteins which are degraded during spore germination. However, the D, E, F, and G proteins were also rapidly degraded during spore germination, accounting for 10 to 15% of the protein degraded. Proteins similar to the D, E, F, and G species were also present in spores of other bacterial species. In B. megaterium, the D, E, F, and G proteins were low or absent (less than 15% of the spore level) in vegetative and young sporulating cells and appeared only late in sporulation. The D, E, F, and G proteins were purified to homogeneity, and all contained a high percentage of hydrophilic amino acids; one protein (G) contained 31% basic amino acids and also contained tryptophan. All four proteins were rapidly degraded in vitro by dormant spore extracts. Two proteins (D and F) were degraded in vitro by the previously described spore protease which initiates degradation of the A, B, and C proteins in vivo; the spore enzyme (s) degrading proteins E and G have not been identified.