Investigations of Thaxtomin Biosynthesis
Abstract
The thaxtomins are dipeptide phytotoxins produced by Streptomyces acidoscabies and related species. A novel feature of these compounds - is the presence of a 4-nitrotryptophan moiety. The thaxtomin gene cluster contains two peptide synthetase genes (txtA; txtB), two cytochrome P450 genes, and a nitric oxide synthase (NOS) gene. The NOS gene is hypothesized to play a role in the formation of 4-nitrotryptophan. Both the mechanism and the timing of the nitration reaction are currently unknown. To determine the timing of the nitration reaction, we cloned the adenylation domains of txtA and txtB, and showed that the proteins can-be overproduced in soluble form in E. coli. This should allow the substrate specificity of these adenylation proteins to be determined in future studies. We also used the NOS gene from the thaxtomin gene cluster to probe several species of Streptomyces that produce metabolites whose biosynthesis might involve a NOS. These investigations led to the cloning of a NOS gene from S. alanosinicus, which produces the antitumor agent L-alanosine. A transformation system was then developed for S. alanosinicus and the NOS gene was disrupted by single crossover insertion. The effect of NOS gene disruption on L-alanosine production is currently under investigation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 2003
- Accession Number
- ADA418760
Entities
People
- Ronald J. Parry
Organizations
- Rice University