Identification of Residues Important for Cleavage of the Extracellular Signaling Peptide, CSF, of B. subtilis From Its' Precursor Protein.

Publication Date: 2008 Aug 8 PMID: 18689487
Authors: Lanigan-Gerdes, S. - Briceno, G. - Dooley, A. N. - Faull, K. F. - Lazazzera, B. A.
Journal: J Bacteriol

Extracellular Phr pentapeptides produced by Gram-positive, spore-forming bacteria regulate processes during transition from exponential to stationary phase growth. Phr pentapeptides are produced by cleavage of their precursor proteins. We determined the residues that direct this cleavage event for the Bacillus subtilis Phr peptide, CSF, which is derived from the C-terminus of PhrC. Strains expressing PhrC with substitutions in the -1 to -5 residues, relative to the cleavage site, had a defect in CSF production. The mutant PhrC proteins retained a functional signal sequence for secretion, as assessed by secretion of PhrC-PhoA fusions. To determine whether these substitutions were directly affecting cleavage of PhrC to CSF, we tested cleavage of synthetic pro-CSF peptides that corresponded to the C-terminus of PhrC and had an amino acid substitution at either the -2, -3, or -4 position. The mutant pro-CSF peptides were cleaved less efficiently to CSF than the wild-type pro-CSF peptide whether incubated with whole cells, cell wall material, or the processing proteases, subtilisin or Vpr. To further define the range of amino acids that would support CSF production, the -4 position of PhrC was substituted with the 19 canonical amino acids. Only four substitutions resulted in greater than a two-fold defect in CSF production, indicating this position is relatively immune to mutational perturbations. These data revealed residues that direct cleavage of CSF and lay the groundwork for testing whether other Phr peptides are processed in a similar manner.

[From Identification of Residues Important for Cleavage of the Extracellular Signaling Peptide, CSF, of B. subtilis From Its' Precursor Protein.]