title: Isolation and characterization of the lantibiotic salivaricin A and its structural gene salA from Streptococcus salivarius 20P3.
abstract: A bacteriocin-like inhibitory substance, salivaricin A, was purified from cultures of Streptococcus salivarius 20P3 and was shown by ion spray mass spectrometry to have a molecular mass of 2,315 +/- 1.1 Da. Amino acid composition analysis demonstrated the presence of lanthionine, indicating that salivaricin A may be a member of the lantibiotic class of antibiotic substances. The sequence of eight amino acids at the N terminus of the molecule was determined by Edman degradation, and mixed oligonucleotide probes based on part of this sequence (GSGWIA) were used to detect the salivaricin A structural gene. A 6.2-kb EcoRI fragment of chromosomal DNA from strain 20P3 that hybridized with the probes was cloned, and the hybridizing region was further localized to a 379-bp DraI-AluI fragment. Analysis of the nucleotide sequence of this fragment indicated that salivaricin A is synthesized as a 51-amino-acid prepeptide that is posttranslationally modified and cleaved to give a biologically active 22-residue peptide containing one lanthionine and two beta-methyllanthionine residues. The secondary structure of presalivaricin A was predicted to be similar to that of type A lantibiotics, with a hydrophilic alpha-helical leader sequence and a propeptide region with potential for beta-turn formation and a lack of alpha-helicity. The sequence around the cleavage site of presalivaricin A differed from that of other type A lantibiotics but was similar to that of several bacteriocin-like inhibitory substances produced by lactic acid bacteria.
authors.affiliation: Department of Microbiology, University of Otago, Dunedin, New Zealand.
authors.forename: K F
authors.initials: KF
authors.lastname: Ross
authors.forename: C W
authors.initials: CW
authors.lastname: Ronson
authors.forename: J R
authors.initials: JR
authors.lastname: Tagg
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives / Q000032:analysis; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D001483:Base Sequence; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics*; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D013291:Streptococcus / Q000737:chemistry* / Q000235:genetics; D013440:Sulfides
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D013440:Sulfides; C082674:salivaricin A; C001520:lanthionine; D000409:Alanine