ElgT1 and ElgT2 may serve as a two-component ABC transporter, similar to MibTU and CinTU, which are probably involved

in the export of microbisporicin and cinnamycin [28, 29]; however this function is uncommon in the maturation of lantibiotics. ElgC encodes a protein containing 454 amino acids, which shows strong homology to the lantibiotic cyclase, MibC, of Microbispora corallina NRRL 30420 (33% identity) [GenBank: ADK32556]. MibC is involved in the formation of (Me)Lan bridges in microbisporicin [28]. The amino acid sequences encoded by the lanC genes have some conserved structural motifs, including GXAHG, WCXG, and CHG, in which the cysteine and histidine residues are highly conserved [30]. The alignment of ElgC with several type AI lantibiotic Selleck Poziotinib synthetases showed that ElgC contains several conserved sequences, such as GVSHG (positions 244-248), WCYG (positions 316-319), and CHG (positions 366-368), wherein His247, Cys317, Cys366, and His367 are strictly conserved. These observations indicate that

ElgC is a lantibiotic synthetase that catalyzes the synthesis of Lan and MeLan residues. A large ORF upstream and overlapping elgT2 by 4 bp encodes a protein of 1037 amino acids. The putative protein ElgB shares 31% identity with MibB of M. corallina NRRL 30420 [GenBank: ADK32555] and 30% identity with SpaB of B. subtilis ATCC 6633 [GenBank: P39774]. The proteins MibB and SpaB are responsible for the dehydration of serine and threonine residues in R428 in vitro the propeptide to form the unsaturated amino acids of microbisporicin and subtilin, respectively [28, 31]. Thus, ElgB appears

to be a dehydratase involved in the process of maturation. Similarly, elgA encodes the prepeptide of the elgicins, with a length of 64 amino acids. No lantibiotics reported thus far share homology with ElgA, suggesting that the mature proteins derived from ElgA are novel lantibiotics. The alignment of the putative leader peptide of ElgA with those of other lantibiotics revealed the existence of a find more possibly conserved motif “”FDLD”" (Figure 1C), which resembles the “”FDLN”" motif in the leader peptide of type AI lantibiotics [32]. Considering that the elg gene cluster contains the lanB and lanC genes encoding the modified enzymes, it could be concluded that the elgicins are type AI lantibiotics. Glycogen branching enzyme The elg gene cluster lacks the immunity genes lanI and lanEFG. LanEFG acts as an ABC transporter for lantibiotic immunity; for example, NisEFG expels lantibiotic molecules that have entered the cytoplasmic membrane into the extracellular environment [33]. Considering the mechanism of LanEFG-imparted immunity, ElgT1T2 is likely to play a role in self-protection, in addition to that of secretion and transportation of the elgicins. The leader peptides of type AI lantibiotics are usually processed by a serine protease encoded by lanP, which is not found in the elg gene cluster. The leader peptide of ElgA may instead be processed by an intrinsic B69 serine protease.