Structure, Biosynthesis, and Bioactivity of Nostolysamides

Area of Science:

• Microbiology
• Biochemistry
• Synthetic Biology

Background:

• Class II lanthipeptides are ribosomally synthesized peptides with complex post-translational modifications.
• Nostoc punctiforme PCC 73102 encodes putative class II lanthipeptides, termed nostolysamides, whose structure and function were previously unknown.

Purpose of the Study:

• To elucidate the structure and bioactivity of nostolysamides.
• To characterize the lanthipeptide synthetase NpuM and the acetyltransferase NpuN involved in nostolysamide biosynthesis.

Main Methods:

• Heterologous expression of nostolysamide precursor peptide and synthetase in Escherichia coli.
• Marfey's analysis for stereochemical determination of modified residues.
• Tandem mass spectrometry and mutagenesis for structural elucidation.
• In vitro assays for enzyme activity and bioactivity testing.

Main Results:

• Nostolysamides were successfully produced and characterized, revealing four lanthionine/methyllanthionine residues with DL configuration.
• NpuM demonstrated dual directionality (C-to-N and N-to-C) in ring formation.
• The mature nostolysamide displayed antibacterial and antifungal activity, acting via cell membrane disruption.
• NpuN acetyltransferase exhibited broad substrate specificity, acylating Lys1, but this modification did not impact the observed bioactivities.

Conclusions:

• Nostolysamides represent a novel class of bioactive lanthipeptides with unique structural features.
• The NpuM synthetase expands the known repertoire of lanthipeptide cyclization mechanisms.
• Acylation by NpuN is a non-essential modification for the antimicrobial and antifungal activities of nostolysamides.