![]() ![]() Left: the enzyme-centric approach pioneered by Marahiel and co-workers. Both of these approaches relied on BLAST searches for colocalized B and C enzymes, followed by a manual search for short open reading frames (ORFs) adjacent to the enzymes ( Figure 2).Īpproaches to lasso peptide genome mining. The first isolation of a new lasso peptide from genome mining approaches followed shortly from the group of Mohamed Marahiel, who published the gene cluster and structure of the antimicrobial lasso peptide capistruin in 2008. The group of Konstantin Severinov, who carried out seminal work in characterizing the antimicrobial function of MccJ25, suggested that gene clusters resembling that of MccJ25 were present in the genomes of several different bacteria, primarily clustered in proteobacteria and actinobacteria. ![]() The first indications of genome mining for lasso peptides appear in the literature in 2007. The colocalization of these genes within a cluster on prokaryotic chromosomes or plasmids is the foundation for lasso peptide genome mining. Finally, the lasso is formed via the action of an asparagine synthetase homolog, the C protein, that presumably both activates the Glu or Asp residue with ATP and templates the lasso structure ( Figure 1). This precursor is processed by a peptidase, the B protein, with a cysteine catalytic triad into leader and core peptides. Like other RiPPs (ribosomally synthesized and post-translationally modified peptides), lasso peptides are born from a precursor peptide, or A protein. This early work laid out the blueprints for lasso peptide biosynthesis. This relatively early example of gene cluster sequencing was facilitated by the fact that the gene cluster for MccJ25 is found on a plasmid. The first lasso peptide gene cluster sequenced was for MccJ25, and appeared in 1999. Like genome mining for other microbial natural products, lasso peptide genome mining depends on the existence of gene clusters encoding the biosynthesis of lasso peptides. We last reviewed this topic in 2014, so this review will focus primarily on new lasso peptide genome mining tools and experimental validation from 2015 onward.Įarly efforts at lasso peptide genome mining ![]() Here instead we focus on genomics-guided approaches for lasso peptide discovery. Lasso peptides that have been discovered by activity-guided approaches have been reviewed elsewhere extensively. Another compelling example of an antimicrobial lasso peptide discovered by activity-guided approaches is lariatin, which has activity against mycobacteria including M. Shortly thereafter, microcin J25 (MccJ25), the most well-studied lasso peptide, was discovered in a search for new antimicrobial compounds in infant fecal bacteria. The first report of a lasso peptide was in 1991 with the discovery of anantin via an activity-based approach. The second macrocycle is generated via a mechanical bond established by threading the C-terminal tail of the peptide through the isopeptide-bonded macrocycle ( Figure 1). The first is formed via a covalent isopeptide bond between the N-terminus of the peptide and either a glutamate or aspartate sidechain. The lasso structure can be thought of as two macrocycles. This slipknotted structure is close in size to many chemically-synthesized rotaxanes and often endows these peptides with proteolytic resistance and thermal resistance. Lasso peptides are a class of ribosomally-derived natural products categorized by their 1-rotaxane structure. ![]()
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