title: Role of the microcin B17 propeptide in substrate recognition: solution structure and mutational analysis of McbA1-26.
abstract: BACKGROUND
  The peptide antibiotic microcin B17 (MccB17) contains oxazole and thiazole heterocycles formed by the post-translational modification of four cysteine and four serine residues. An amino-terminal propeptide targets the 69 amino acid precursor of MccB17 (preproMccB17) to the heterocyclization enzyme MccB17 synthetase. The mode of synthetase recognition has been unclear, because there has been limited structural information available on the MccB17 propeptide to date.
  
  
  RESULTS
  The solution structure of the MccB17 propeptide (McbA1-26), determined using nuclear magnetic resonance, reveals that McbA1-26 is an amphipathic alpha helix. Mutational analysis of 13 propeptide residues showed that Phe8 and Leu12 are essential residues for MccB17 synthetase recognition. A domain of the propeptide was putatively identified as the region that interacts with the synthetase.
  
  
  CONCLUSIONS
  MccB17 synthetase recognizes key hydrophobic residues within a helical propeptide, allowing the selective heterocyclization of downstream cysteine and serine residues in preproMccB17. The determination of the solution structure of the propeptide should facilitate the investigation of other functions of the propeptide, including a potential role in antibiotic secretion.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: R S
authors.initials: RS
authors.lastname: Roy
authors.forename: S
authors.initials: S
authors.lastname: Kim
authors.forename: J D
authors.initials: JD
authors.lastname: Baleja
authors.forename: C T
authors.initials: CT
authors.lastname: Walsh
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry*; D001426:Bacterial Proteins; D001430:Bacteriocins / Q000737:chemistry* / Q000235:genetics; D001665:Binding Sites; D009097:Multienzyme Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D011498:Protein Precursors / Q000737:chemistry* / Q000235:genetics; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001430:Bacteriocins; D009097:Multienzyme Complexes; D010455:Peptides; D011498:Protein Precursors; C102057:microcin B17 synthase; C020411:microcin