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4‐Nitrotryptophan is a substrate for the non‐ribosomal peptide synthetase TxtB in the thaxtomin A biosynthetic pathway
Author(s) -
Johnson Evan G.,
Krasnoff Stuart B.,
Bignell Dawn R. D.,
Chung WenChuan,
Tao Tao,
Parry Ronald J.,
Loria Rosemary,
Gibson Donna M.
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.1365-2958.2009.06780.x
Subject(s) - biology , adenylylation , mutant , biosynthesis , biochemistry , ribosomal protein , peptide , ribosomal rna , 23s ribosomal rna , streptomyces coelicolor , streptomyces , moiety , enzyme , stereochemistry , genetics , bacteria , gene , ribosome , chemistry , rna
Summary Thaxtomin A, a cyclic dipeptide with a nitrated tryptophan moiety, is a phytotoxic pathogenicity determinant in scab‐causing Streptomyces species that inhibits cellulose synthesis by an unknown mechanism. Thaxtomin A is produced by the action of two non‐ribosomal peptide synthetase modules (TxtA and TxtB) and a complement of modifying enzymes, although the order of biosynthesis has not yet been determined. Analysis of a thaxtomin dual module knockout mutant and single module knockout mutants revealed that 4‐nitrotryptophan is an intermediate in thaxtomin A biosynthesis prior to backbone assembly. The 4‐nitrotryptophan represents a novel substrate for non‐ribosomal peptide synthetases. Through identification of N ‐methyl‐4‐nitrotryptophan in a single module knockout and the use of adenylation domain specificity prediction software, TxtB was identified as the non‐ribosomal peptide synthetase module specific for 4‐nitrotryptophan.