Bacterial Labionin-Containing Peptides and Sactibiotics: Unusual Types of Antimicrobial Peptides with Potential Use in Clinical Settings (a Review)

One of the biggest challenges faced presently by clinicians is the emergence of multidrug -resistant pathogens that can infect humans and animals. To control the infections caused by such pathogens the development of new drugs is required. Bacteria are a rich source of ribosomally -synthesized antimicrobial peptides known as bacteriocins, which are characterized by the presence of a self-defense immunity system. Labionin-containing lantibiotics and sactibiotics are posttranslationally modified bacteriocins with peculiar features. Labionin-containing peptides belong to subclass Ic lantibiotics in which the carbacyclic triamino triacid labionin, a structural variant of lanthionine, and a methyl-substitute labionin derivative are found, giving the molecule a labyrinthine structure. Sactibiotics are circular or linear peptides belonging to a distinct bacteriocin class (class V) which is characterized by the presence of cross-linkages formed by the thiol group of cysteine residues and the α-carbon of acceptor amino acids. A few examples of these bacteriocins have been described in the literature to date, although putative gene clusters with the potential to encode such peptides can be found in the genome of many bacterial species. Some peptides already under study exhibit potential biotechnological applications because of their remarkable antibacterial or antiviral activities, as well as their analgesic activity. Therefore, in this review, the main findings concerning these peptides will be addressed and discussed, with an emphasis on their potential use in clinical settings.