Premium
The non‐ribosomal assembly and frequent occurrence of the protease inhibitors spumigins in the bloom‐forming cyanobacterium Nodularia spumigena
Author(s) -
Fewer David P.,
Jokela Jouni,
Rouhiainen Leo,
Wahlsten Matti,
Koskenniemi Kerttu,
Stal Lucas J.,
Sivonen Kaarina
Publication year - 2009
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2009.06816.x
Subject(s) - biology , cyanobacteria , ribosomal rna , algal bloom , microbiology and biotechnology , protease , prokaryote , peptide , biochemistry , enzyme , bacteria , gene , genetics , ecology , phytoplankton , nutrient
Summary Nodularia spumigena is a filamentous nitrogen‐fixing cyanobacterium that forms toxic blooms in brackish water bodies worldwide. Spumigins are serine protease inhibitors reported from a single strain of N. spumigena isolated from the Baltic Sea. These linear tetrapeptides contain non‐proteinogenic amino acids including a C‐terminal alcohol derivative of arginine. However, very little is known about these compounds despite the ecological importance of N. spumigena . We show that spumigins are assembled by two non‐ribosomal peptide synthetases encoded in a 21 kb biosynthetic gene cluster. The compact non‐ribosomal peptide synthetase features a reductive loading and release mechanism. Our analyses demonstrate that the bulk of spumigins produced by N. spumigena are released as peptide aldehydes in contrast to earlier findings. The main spumigin E variant contains an argininal residue and is a potent trypsin inhibitor. Spumigins were present in all of the N. spumigena strains isolated from the Baltic Sea and comprised up to 1% of the dry weight of the cyanobacterium. Our results demonstrate that bloom‐forming N. spumigena strains produce a cocktail of enzyme inhibitors, which may explain in part the ecological success of this cyanobacterium in brackish water bodies worldwide.