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SpoIIGA is a novel type of membrane-associated aspartic protease that responds to a signal from the forespore by cleaving Pro-σE in the mother cell during sporulation of Bacillus subtilis. Very little is known about how SpoIIGA recognizes Pro-σE. By co-expressing proteins in Escherichia coli, it was shown that charge reversal substitutions for acidic residues 24 and 25 of Pro-σE, and for basic residues 245 and 284 of SpoIIGA, impaired cleavage. These results are consistent with a model predicting possible electrostatic interactions between these residues; however, no charge reversal substitution for residue 245 or residue 284 of SpoIIGA restored cleavage of Pro-σE with a charge reversal substitution for residue 24 or residue 25. Bacillus subtilis SpoIIGA cleaved Pro-σE orthologs from Bacillus licheniformis and Bacillus halodurans, but not from Bacillus cereus. A triple substitution in the pro-sequence of B. cereus Pro-σE allowed cleavage by B. subtilis SpoIIGA, indicating that residues distal from the cleavage site contribute to substrate specificity. Co-expression of SpoIIGA and Pro-σE orthologs in different combinations suggested that B. licheniformis SpoIIGA has a relatively narrow substrate specificity as compared with B. subtilis SpoIIGA, whereas B. cereus SpoIIGA and B. halodurans SpoIIGA appear to have broader substrate specificity. [ABSTRACT FROM PUBLISHER]

The article presents a study on the involvement of a Bacillus subtilis-derived novel protein in spore germination and spore coat assembly. It mentions that the SscA-FLAG fusion protein was produced from sporulation of mature plant spores. It notes that SscA is involved in the formation of several components of spore coats including CotB, CotG and CotH.