Structural Analysis and Characterization of Lacticin Q, a Novel Bacteriocin Belonging to a New Family of Unmodified Bacteriocins of Gram-Positive Bacteria

Abstract

Lactococcus lactis QU 5 isolated from corn produces a novel bacteriocin, termed lacticin Q. By acetone precipitation, cation-exchange chromatography, and reverse-phase high-performance liquid chromatography, lacticin Q was purified from the culture supernatant of this organism, and its molecular mass was determined to be 5,926.50 Da by mass spectrometry. Subsequent analyses of amino acid and DNA sequences revealed that lacticin Q comprised 53 amino acid residues and that its N-terminal methionine residue was formylated. In contrast to most bacteriocins produced by gram-positive bacteria, lacticin Q had no N-terminal extensions such as leader or signal sequences. It showed 66% and 48% identity to AucA, a hypothetical protein from Corynebacterium jeikeium plasmid pA501, and aureocin A53, a bacteriocin from Staphylococcus aureus A53, respectively. The characteristics of lacticin Q were determined and compared to those of nisin A. Similar to nisin A, lacticin Q exhibited antibacterial activity against various grampositive bacteria. Lacticin Q was very stable against heat treatment and changes in pH; in particular, it was stable at alkaline pH values, while nisin A was inactivated. Moreover, lacticin Q induced ATP efflux from a Listeria sp. strain in a shorter time and at a lower concentration than nisin A, indicating that the former affected indicator cells in a different manner from that of the latter. The results described here clarified the fact that lacticin Q belongs to a new family of class II bacteriocins and that it can be employed as an alternative to or in combination with nisin A.Bacteriocins are ribosomally synthesized antimicrobial peptides or proteins that are active against closely related species (17). Those produced by lactic acid bacteria (LAB) have attracted increasing interest in terms of their safety since many LAB are generally regarded as safe (GRAS) (7). Bacteriocins produced by gram-positive bacteria, including LAB, are mainly classified into three classes (18,26). Class I bacteriocins, the so-called lantibiotics, are heat-stable post-translationally modified peptides that contain multiple rings bridged by lanthionine or 3-methyllanthionine residues (22). Class II bacteriocins are small heat-stable nonlantibiotic peptides and are in turn divided into three subgroups (25, 26). Class IIa bacteriocins are Listeria sp.-active peptides with a consensus YGNGVXC sequence at their N termini (10). Class IIb bacteriocins comprise two peptides, both of which are required for complete antibacterial activity. Class IIc bacteriocins are the other class II bacteriocins; this subclass includes enterocin P, which is processed and secreted by the Sec pathway (4), and enterocin L50 (5), which is secreted without a leader sequence. However, some class II bacteriocins can be placed in more than one subclass, while others do not fit easily into any of the subclasses (27).Class III bacteriocins are heat-labile proteins, including millericin B, that hydrolyze specific peptide bonds in the stem and/or interpeptide b...

Characterization and identification of weissellicin Y and weissellicin M, novel bacteriocins produced by Weissella hellenica QU 13

“…Most LAB bacteriocins were synthesized as prepeptides containing N-terminal extension or leader sequences, while some class II bacteriocins have been reported to be synthesized without a leader sequence. The latter includes mutacin BHT-B (Hyink et al 2005), lacticin Q (Fujita et al 2007), lacticin Z (Iwatani et al 2007), enterocin Q (Cintas et al 2000) and enterocin L50 (Cintas et al 1998;Criado et al 2006a;Izquierdo et al 2008), most of which are class IId bacteriocins.…”

“…DNA manipulations were performed according to the previous report (Fujita et al 2007). DNA polymerases, restriction enzymes and other DNA-modifying enzymes were used according to the manufacturer's instructions.…”

“…DNA polymerases, restriction enzymes and other DNA-modifying enzymes were used according to the manufacturer's instructions. Total DNA of strain QU 13 was extracted from cells treated with lysozyme (Seikagaku, Tokyo, Japan) and cetyltrimethylammonium bromide (Wako, Osaka, Japan), according to procedures described previously (Fujita et al 2007), and used as a template for PCR and subsequent procedures. The oligonucleotide primers used in this study are listed in Table 1.…”

Bacteriocins from Lactic Acid Bacteria: A Review of Biosynthesis, Mode of Action, Fermentative Production, Uses, and Prospects

“…On the other hand, class IId bacteriocins comprise the remaining bacteriocins that are combined as miscellaneous or one-peptide nonpediocin linear group (Cotter et al 2005;Iwatani et al 2011;Masuda et al 2012). Sec-dependent bacteriocins (Cintas et al 2000) and the growing number of bacteriocins that do not have leader peptides and therefore known as leaderless bacteriocins (Fujita et al 2007), belong to this class.…”

Effect of a Negatively Charged Lipid on Membrane-Lacticin Q Interaction and Resulting Pore Formation

“…7) Lacticin Q consists of 53 amino acids containing abundant cationic and hydrophobic residues. As in the case of nisin, lacticin Q exerts its killing activity in the nanomolar range only against Gram-positive bacteria, and not against blood cells, but it does not need any specific receptors for pore-forming activity.…”