Substrate specificity of SpoIIGA, a signal-transducing aspartic protease in Bacilli.

ABSTRACT: SpoIIGA is a novel type of membrane-associated aspartic protease that responds to a signal from the forespore by cleaving Pro-?(E) in the mother cell during sporulation of Bacillus subtilis. Very little is known about how SpoIIGA recognizes Pro-?(E). By co-expressing proteins in Escherichia coli, it was shown that charge reversal substitutions for acidic residues 24 and 25 of Pro-?(E), 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-?(E) with a charge reversal substitution for residue 24 or residue 25. Bacillus subtilis SpoIIGA cleaved Pro-?(E) orthologs from Bacillus licheniformis and Bacillus halodurans, but not from Bacillus cereus. A triple substitution in the pro-sequence of B. cereus Pro-?(E) allowed cleavage by B. subtilis SpoIIGA, indicating that residues distal from the cleavage site contribute to substrate specificity. Co-expression of SpoIIGA and Pro-?(E) 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.

SUBMITTER: Imamura D 

PROVIDER: S-EPMC3143438 | biostudies-literature | 2011 Jun

REPOSITORIES: biostudies-literature