Enterocin P precursor

Genome sequencing of Enterococcus faecium M3K31, a strain isolated from griffon vultures, previously revealed the presence of three sequences encoding for bacteriocins, namely enterocin P, enterocin HF, and a SRCAM 602-like bacteriocin. In this work, we describe the SRCAM 602-like bacteriocin that we named faerocin MK. Mature faerocin MK consists of 43 residues and contains an YGNGV-motif and two cysteine residues at positions 10 and 15, consistent with other class IIa bacteriocins. Faerocin MK and SRCAM 602 were chemically synthesized and their scope of activity was tested. Faerocin MK is active against a wide range of Gram-positive organisms while SRCAM 602 was not active against any tested organism. Although both peptides are more structured in trifluoroethanol, faerocin MK has an α-helical character nearly twice that of SRCAM 602. Nucleotide sequence analysis revealed that the faerocin MK precursor is produced with a 28-amino acid signal peptide and that an immunity gene follows the structural faerocin MK gene. Heterologous expression of the faerocin MK operon showed that faerocin MK and its immunity protein were successfully expressed in other organisms. This indicates that the bacteriocin is secreted through the sec pathway.

Bacteriocins are ribosomally synthesized antibacterial peptides or proteins from microorganisms. We report a novel bacteriocin producing strain, Enterococcus faecalis Gr17, that was isolated from the Chinese traditional low-salt fermented whole fish product Suan yu. E. faecalis Gr17 displayed potent antibacterial activity against foodborne pathogenic and spoilage bacteria. The complete genome of E. faecalis Gr17 contained one circular chromosome and plasmid. The gene cluster of a novel bacteriocin designated enterocin Gr17 was identified. The enterocin Gr17 structural gene encodes a precursor of the bacteriocin. Two other transporter genes and an immunity gene within two divergent operons were identified as being associated with enterocin Gr17 secretion and protection. The novel enterocin Gr17 was purified by ammonium sulfate precipitation, cation exchange, gel filtration, and reverse-phase high-performance liquid chromatography. The molecular weight of enterocin Gr17 was 4,531.01 Da as determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and its mature amino acid sequence of enterocin Gr17 was RSYGNGVYCNNSKCWVNWGEAKENIIGIVISGWATGLAGMGR. Sequence alignment revealed that enterocin Gr17 is a class IIa bacteriocin with similarities to enterocin P. The merits of bactericidal activity, sensitivity to enzymes, and pronounced stability to chemicals, temperature (60°C, 30 min and 121°C, 15 min), and pH (2-10) indicated practicality and safety of enterocin Gr17 in the food industry. The complete genome information of E. faecalis Gr17 will improve the understanding of the biosynthetic mechanism of enterocin Gr17, which has potential value as a food biopreservative.