The Bacillus subtilis signaling protein SpoIVB defines a new family of serine peptidases.
The protein SpoIVB plays a key role in signaling in the final sigma(K) checkpoint of Bacillus subtilis. This regulatory mechanism coordinates late gene expression during development in this organism and we have recently shown SpoIVB to be a serine peptidase. SpoIVB signals by transiting a membrane, undergoing self-cleavage, and then by an unknown mechanism activating a zinc metalloprotease, SpoIVFB, which cleaves pro-final sigma(K) to its active form, final sigma(K), in the outer mother cell chamber of the developing cell. In this work we have characterized the serine peptidase domain of SpoIVB. Alignment of SpoIVB with homologues from other spore formers has allowed site-specific mutagenesis of all potential active site residues within the peptidase domain. We have defined the putative catalytic domain of the SpoIVB serine peptidase as a 160-amino-acid residue segment at the carboxyl terminus of the protein. His236 and Ser378 are the most important residues for proteolysis, with Asp363 being the most probable third member of the catalytic triad. In addition, we have shown that mutations at residues Asn290 and His394 lead to delayed signaling in the final sigma(K) checkpoint. The active site residues suggest that SpoIVB and its homologues from other spore formers are members of a new family of serine peptidases of the trypsin superfamily.
Hoa
Ngo T
NT
School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, United Kingdom.
Brannigan
James A
JA
Cutting
Simon M
SM
D000595:Amino Acid Sequence; D001224:Aspartic Acid / Q000235:genetics; D001412:Bacillus subtilis / Q000201:enzymology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain / Q000235:genetics; D017124:Conserved Sequence; D006639:Histidine / Q000235:genetics; D008239:Lysine / Q000235:genetics; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011499:Protein Processing, Post-Translational; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000235:genetics; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013171:Spores, Bacterial / Q000201:enzymology; D014157:Transcription Factors / Q000378:metabolism
D001426:Bacterial Proteins; D008565:Membrane Proteins; D014157:Transcription Factors; C084190:sigma K; C088067:spoIV protein, Bacillus megaterium; D001224:Aspartic Acid; D012694:Serine; D006639:Histidine; D012697:Serine Endopeptidases; D008239:Lysine