title: Effect of amino acid substitutions in conserved residues in the leader peptide on biosynthesis of the lantibiotic mutacin II.
abstract: The lantibiotic mutacin II, produced by Streptococcus mutans T8, is a ribosomally synthesized peptide antibiotic that contains thioether amino acids such as lanthionine and methyllanthionine as a result of post-translational modifications. The mutacin II leader peptide sequence shares a number of identical amino acid residues with class AII lantibiotic leader peptides. To study the role of these conservative residues in the production of active antimicrobial mutacin, 15 mutations were generated by site-directed mutagenesis. The effects of these substitutions vary from no effect to complete block-out. Mutations G-1A, G-2A, I-4D, and L-7K completely blocked the production of mature mutacin. Other mutations (I-4V, L-7M, E-8D, S-11T/A, V-12I/A, and E-13D) had no detectable effect on mutacin production. The changes of Glu-8 to Lys, Val-12 to Leu, Glu-13 to Lys reduced the mutacin production level to about 75%, 50%, and 10% of the wild-type, respectively. Thus, our data indicated that some of these conserved residues are essential for the mutacin biosynthesis, whereas others are important for optimal biosynthesis rates.
authors.affiliation: LHRB 250, Department of Oral Biology, University of Alabama at Birmingham, 1919 7th Avenue South, Birmingham, AL 35294, USA. pichenjx@uab.edu
authors.forename: P
authors.initials: P
authors.lastname: Chen
authors.forename: F X
authors.initials: FX
authors.lastname: Qi
authors.forename: J
authors.initials: J
authors.lastname: Novak
authors.forename: R E
authors.initials: RE
authors.lastname: Krull
authors.forename: P W
authors.initials: PW
authors.lastname: Caufield
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001430:Bacteriocins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011498:Protein Precursors / Q000096:biosynthesis; D021382:Protein Sorting Signals / Q000235:genetics; D013295:Streptococcus mutans / Q000235:genetics / Q000378:metabolism*
chemical_list: D001430:Bacteriocins; D011498:Protein Precursors; D021382:Protein Sorting Signals; C069066:mutacin II