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Dysgalacticin: a novel, plasmid-encoded antimicrobial protein (bacteriocin) produced by Streptococcus dysgalactiae subsp. equisimilis
- Source :
- Microbiology. July, 2006, Vol. 152 Issue 7, p1991, 11 p.
- Publication Year :
- 2006
-
Abstract
- Dysgalacticin is a novel bacteriocin produced by Streptococcus dysgalactiae subsp, equisimilis strain W2580 that has a narrow spectrum of antimicrobial activity directed primarily against the principal human streptococcal pathogen Streptococcus pyogenes. Unlike many previously described bacteriocins of Gram-positive bacteria, dysgalacticin is a heat-labile 21.5 kDa anionic protein that kills its target without inducing lysis. The N-terminal amino acid sequence of dysgalacticin [Asn-Glu-Thr-Asn-Asn-Phe-Ala-Glu-Thr-Gln -Lys-Glu-lle-Thr-Thr-Asn-(Asn)-Glu-Ala] has no known homologue in publicly available sequence databases. The dysgalacticin structural gene, dysA, is located on the indigenous plasmid pW2580 of strain W2580 and encodes a 220 aa preprotein which is probably exported via a Sec-dependent transport system. Natural dysA variants containing conservative amino acid substitutions were also detected by sequence analyses of dysA elements from S. dysgalactiae strains displaying W2580-1ike inhibitory profiles. Production of recombinant dysgalacticin by Escherichia coli confirmed that this protein is solely responsible for the inhibitory activity exhibited by strain W2580. A combination of in silico secondary structure prediction and reductive alkylation was employed to demonstrate that dysgalacticin has a novel structure containing a disulphide bond essential for its biological activity. Moreover, dysgalacticin displays similarity in predicted secondary structure (but not primary amino acid sequence or inhibitory spectrum) with another plasmid-encoded streptococcal bacteriocin, streptococcin A-M57 from S. pyogenes, indicating that dysgalacticin represents a prototype of a new class of antimicrobial proteins.
- Subjects :
- Streptococcus -- Genetic aspects
Plasmids -- Research
Biological sciences
Subjects
Details
- Language :
- English
- ISSN :
- 13500872
- Volume :
- 152
- Issue :
- 7
- Database :
- Gale General OneFile
- Journal :
- Microbiology
- Publication Type :
- Academic Journal
- Accession number :
- edsgcl.149364499