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Salivaricin A2 and the novel lantibiotic salivaricin B are encoded at adjacent loci on a 190-kilobase transmissible megaplasmid in the oral probiotic strain Streptococcus salivarius K12.

ABSTRACT: The commercial probiotic Streptococcus salivarius strain K12 is the prototype of those S. salivarius strains that are the most strongly inhibitory in a standardized test of streptococcal bacteriocin production and has been shown to produce the 2,368-Da salivaricin A2 (SalA2) and the 2,740-Da salivaricin B (SboB) lantibiotics. The previously uncharacterized SboB belongs to the type AII class of lantibiotic bacteriocins and is encoded by an eight-gene cluster. The genetic loci encoding SalA2 and SboB in strain K12 have been fully characterized and are localized to nearly adjacent sites on pSsal-K12, a 190-kb megaplasmid. Of 61 strongly inhibitory strains of S. salivarius, 19 (31%) were positive for the sboB structural gene. All but one (strain NR) of these 19 strains were also positive for salA2, and in each of these cases of double positivity, the two loci were separated by fewer than 10 kb. This is the first report of a single streptococcus strain producing two distinct lantibiotics.

SUBMITTER: Hyink O

PROVIDER: S-EPMC1828679 | biostudies-literature | 2007 Feb

REPOSITORIES: biostudies-literature

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Salivaricin A2 and the novel lantibiotic salivaricin B are encoded at adjacent loci on a 190-kilobase transmissible megaplasmid in the oral probiotic strain Streptococcus salivarius K12.

Hyink Otto O Wescombe Philip A PA Upton Mathew M Ragland Nancy N Burton Jeremy P JP Tagg John R JR

Applied and environmental microbiology 20061228 4

The commercial probiotic Streptococcus salivarius strain K12 is the prototype of those S. salivarius strains that are the most strongly inhibitory in a standardized test of streptococcal bacteriocin production and has been shown to produce the 2,368-Da salivaricin A2 (SalA2) and the 2,740-Da salivaricin B (SboB) lantibiotics. The previously uncharacterized SboB belongs to the type AII class of lantibiotic bacteriocins and is encoded by an eight-gene cluster. The genetic loci encoding SalA2 and S ...[more]

PMID: 17194838

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Project description:Lantibiotics are a class of lanthionine-containing, ribosomally synthesized, and posttranslationally modified peptides (RiPPs) produced by Gram-positive bacteria. Salivaricin A2 belongs to the type AII lantibiotics, which are generally considered to kill Gram-positive bacteria by binding to the cell wall precursor lipid II via a conserved ring A structure. Salivaricin A2 was first reported to be isolated from a probiotic strain, Streptococcus salivarius K12, but the structural and bioactivity characterizations of the antibiotic have remained limited. In this study, salivaricin A2 was purified and its covalent structure was characterized. N-terminal analogues of salivaricin A2 were generated to study the importance for bioactivity of the length and charge of the N-terminal amino acids. Analogue salivaricin A2(3-22) has no antibacterial activity and does not have an antagonistic effect on the native compound. The truncated analogue also lost its ability to bind to lipid II in a thin-layer chromatography (TLC) assay, suggesting that the N-terminal amino acids are important for binding to lipid II. The creation of N-terminal analogues of salivaricin A2 promoted a better understanding of the bioactivity of this antibiotic and further elucidated the structural importance of the N-terminal leader peptide. The antibacterial activity of salivaricin A2 is due not only to the presence of the positively charged N-terminal amino acid residues, but to the length of the N-terminal linear peptide.IMPORTANCE The amino acid composition of the N-terminal linear peptide of salivaricin A2 is crucial for function. Our study shows that the length of the amino acid residues in the linear peptide is crucial for salivaricin A2 antimicrobial activity. Very few type AII lantibiotic covalent structures have been confirmed. The characterization of the covalent structure of salivaricin A2 provides additional support for the predicted lanthionine and methyl-lanthionine ring formations present in this structural class of lantibiotics. Removal of the N-terminal Lys1 and Arg2 residues from the peptide causes a dramatic shift in the chemical shift values of amino acid residues 7 through 9, suggesting that the N-terminal amino acids contribute to a distinct structural conformer for the linear peptide region. The demonstration that the bioactivity could be partially restored with the substitution of N-terminal alanine residues supports further studies aimed at determining whether new analogues of salivaricin A2 for novel applications can be synthesized.

Dataset Information

Salivaricin A2 and the novel lantibiotic salivaricin B are encoded at adjacent loci on a 190-kilobase transmissible megaplasmid in the oral probiotic strain Streptococcus salivarius K12.

Publications

Salivaricin A2 and the novel lantibiotic salivaricin B are encoded at adjacent loci on a 190-kilobase transmissible megaplasmid in the oral probiotic strain Streptococcus salivarius K12.

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