ABSTRACT
UstYa family proteins (DUF3328) are widely and specifically distributed in fungi. They are known to be involved in the biosynthesis of ribosomally synthesized and posttranslationally modified peptides (RiPPs) and nonribosomal peptides, and possibly catalyze various reactions, including oxidative cyclization and chlorination. In this study, we focused on phomopsinâ A, a fungal RiPP consisting of unique nonproteinogenic amino acids. Gene knockout experiments demonstrated that three UstYa homologues, phomYc, phomYd, and phomYe, are essential for the desaturation of amino acid moieties, showing unprecedented function among UstYa family proteins. Sequence similarity network analysis indicated that their amino acid sequences are highly diverged and that most remain uncharacterized, paving the way for genome mining of fungal metabolites with unique modifications.
Subject(s)
Amino Acids/metabolism , Fungal Proteins/metabolism , Mycotoxins/biosynthesis , Amino Acids/chemistry , Aspergillus oryzae/chemistry , Fungal Proteins/chemistry , Molecular Structure , Mycotoxins/chemistry , Protein Processing, Post-TranslationalABSTRACT
Mycotoxin cyclochlorotine (1) and structurally related astins are cyclic pentapeptides containing unique nonproteinogenic amino acids, such as ß-phenylalanine, l-allo-threonine, and 3,4-dichloroproline. Herein, we report the biosynthetic pathway for 1, which involves intriguing tailoring processes mediated by DUF3328 proteins, including stereo- and regiospecific chlorination and hydroxylation and intramolecular O,N-transacylation. Our findings demonstrate that DUF3328 proteins, which are known to be involved in oxidative cyclization of fungal ribosomal peptides, have much higher functional diversity than previously expected.
Subject(s)
Fungal Proteins/genetics , Mycotoxins/chemistry , Peptides, Cyclic/biosynthesis , Phenylalanine/chemistry , Acylation , Amino Acids/metabolism , Biosynthetic Pathways , Cyclization , Hydroxylation , Molecular Structure , Mycotoxins/metabolism , Oxidation-Reduction , Peptides, Cyclic/chemistryABSTRACT
The biosynthetic machinery of the first fungal ribosomally synthesized and post-translationally modified peptide (RiPP) ustiloxinâ B was elucidated through a series of gene inactivation and heterologous expression studies. The results confirmed an essential requirement for novel oxidases possessing the DUF3328 motif for macrocyclization, and highly unique side-chain modifications by three oxidases (UstCF1F2) and a pyridoxal 5'-phosphate (PLP)-dependent enzyme (UstD). These findings provide new insight into the expression of the RiPP gene clusters found in various fungi.
