title: Complex formation and processing of the minor transformation pilins of Bacillus subtilis.
abstract: Transformation in most bacteria is dependent on orthologues of Type 2 secretion and Type 4 pilus system proteins. In each system, pilin proteins (major and minor) are required to make the pilus structure and are essential to the process, although the precise roles of the minor pilins remain unclear. We have explored protein-protein interactions among the competence minor pilins of Bacillus subtilis through in vitro binding studies, immunopurification and mass spectrometry. We demonstrate that the minor pilins directly interact, and the minor pilin ComGG interacts with most of the known proteins required for transformation. We find that ComGG requires other ComG proteins for its stabilization and for processing by the pre-pilin peptidase. These observations, C-terminal mutations in ComGG that prevent processing and the inaccessibility of pre-ComGG to externally added protease suggest a model in which pre-ComGG must be associated with other minor pilins for processing to take place. We propose that ComGG does not become a transmembrane protein until after processing. These behaviours contrast with that of pre-ComGC, the major pilin, which is accessible to externally added protease and requires only the peptidase to be processed. The roles of the pilins and of the pilus in transformation are discussed.
authors.affiliation: Department of Microbiology and Molecular Genetics, New Jersey Medical School, Rutgers University, 225 Warren Street, Newark, NJ, 07103, USA.
authors.forename: Jessica M
authors.initials: JM
authors.lastname: Mann
authors.forename: Valerie J
authors.initials: VJ
authors.lastname: Carabetta
authors.forename: Ileana M
authors.initials: IM
authors.lastname: Cristea
authors.forename: David
authors.initials: D
authors.lastname: Dubnau
mesh_terms: D001412:Bacillus subtilis / Q000235:genetics* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D036781:Fimbriae Proteins / Q000235:genetics / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000378:metabolism*; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010447:Peptide Hydrolases / Q000378:metabolism*; D055550:Protein Stability; D014169:Transformation, Bacterial
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D036781:Fimbriae Proteins; D010447:Peptide Hydrolases