Abstract
Lantibiotics are (methyl)-lanthionine-containing antimicrobial peptides produced by several Gram-positive bacteria. Some human pathogenic bacteria express specific resistance proteins that counteract this antimicrobial activity of lantibiotics. In Streptococcus agalactiae COH1 resistance against the well-known lantibiotic nisin is conferred by, the nisin resistance protein (NSR), a two-component system (NsrRK) and a BceAB-type ATP-binding cassette (ABC) transporter (NsrFP). The present study focuses on elucidating the function of NsrFP via its heterologous expression in Lactococcus lactis. NsrFP is able to confer a 16-fold resistance against wild type nisin as determined by growth inhibition experiments and functions as a lantibiotic exporter. Several C-terminal nisin mutants indicated that NsrFP recognizes the N-terminal region of nisin. The N-terminus harbors three (methyl)-lanthionine rings, which are conserved in other lantibiotics.
Highlights
Lantibiotics are ribosomally synthesized antimicrobial peptides of approximately 19–38 amino acids, which are mainly produced by Gram-positive bacteria (Klaenhammer, 1993)
We focused on the lantibiotic nisin, which is produced by some Lactococcus lactis and Streptococcus uberis strains (Klaenhammer, 1993; Chatterjee et al, 2005)
The nsrfp gene from S. agalactiae COH1 was amplified from the chromosomal DNA using two primers (NsrFP_for 5 -CA TCACCACCACCACTTATTAGAAATCAATCACTTAG-3 and NsrFP_rev 5 -GTGGTGGTGGTGGTGCATATAATTCTCCTTTA TTTATTATAC-3) and ligated into pIL-SV (E. coli–L. lactis shuttle vector) (Alkhatib et al, 2014b)
Summary
Lantibiotics are ribosomally synthesized antimicrobial peptides of approximately 19–38 amino acids, which are mainly produced by Gram-positive bacteria (Klaenhammer, 1993). Within the human pathogen Streptococcus agalactiae COH1 the expression of a proteogenous resistance system comprising of NSR (nisin resistance protein; a serine protease), an ATP-binding cassette (ABC) transporter (NsrFP) and a two-component system (TCS) (NsrRK) confers resistance against nisin (Khosa et al, 2013). This NSR operon has been characterized biochemically and structurally. This was confirmed by the observed resistance against nisin H (O’Connor et al, 2015) and gallidermin (Kellner et al, 1988), which both contain a similar N-terminus but differ in the C-terminal part of the peptide
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