Mechanistic Insights Into Post-translational α-Keto-β-Amino Acid Formation by a Radical S-Adenosyl Methionine Peptide Splicease.

Radical S-adenosyl methionine enzymes catalyze a diverse repertoire of post-translational modifications in protein and peptide substrates. Among these, an exceptional and mechanistically obscure example is the installation of α-keto-β-amino acid residues by formal excision of a tyrosine-derived tyramine unit. The responsible spliceases are key maturases in a widespread family of natural products termed spliceotides that comprise potent protease inhibitors, with the installed β-residues being crucial for bioactivity.

Ribosomal peptides with polycyclic isoprenoid moieties.

Isoprenoid modifications of proteins and peptides serve fundamental biological functions and are of therapeutic interest. While C (farnesyl) and C (geranylgeranyl) moieties are prevalent among proteins, known ribosomal peptide prenylations involve shorter-chain units not exceeding farnesyl in size. To our knowledge, cyclized terpene moieties have not been reported from either biomolecule class.

Porin-independent accumulation in Pseudomonas enables antibiotic discovery.

Gram-negative antibiotic development has been hindered by a poor understanding of the types of compounds that can accumulate within these bacteria. The presence of efflux pumps and substrate-specific outer-membrane porins in Pseudomonas aeruginosa renders this pathogen particularly challenging. As a result, there are few antibiotic options for P.

A cylindrospermopsin-producing cyanobacterium isolated from a microbial mat in the Baltic Sea.

Toxic benthic mats of cyanobacteria are associated with water quality problems and animal poisonings around the world. A strain of the filamentous cyanobacterial genus Kamptonema was isolated from a water bloom in the Baltic Sea four decades ago and later shown to produce cylindrospermopsins. However, the exact habitat of this strain remains unclear and cylindrospermopsins have not yet been reported from water blooms in the Baltic Sea.