BIOSYNTHESIS OF SOME MICROBIAL METABOLITES

Summary

Principal Investigator: R J Parry
Affiliation: Rice University
Country: USA
Abstract: Investigations of the biosynthesis of two novel microbial metabolites will be continued. The first is the antitumor agent valanimycin, an azoxy compound produced by S. viridifaciens. This compound is important because its damages DNA, and because it containan N-N bond. Although natural products containing N-N bonds are widely distributed, little is known about the mechanism(s) of N-N bond formation. Previous studies of valanimycin biosynthesis revealed some steps in the biosynthetic pathway and led to the isolation of a cosmid containing all of the genes required for valanimycin biosynthesis. Future studies of valanimycin have several goals. The first is to finish the sequencing and analysis of the genes required for valanimycin production. The second is to identify the gene(s) required for N-N bond formation by sequence analysis, and non-polar gene disruptions. The third is to overproduce the protein(s) required for N-N bond formation and examine the N-N bond forming chemistry in vitro. The fourth is to further characterize putative valanimycin resistance gene. The fifth goal is to complete studies of the two-component flavin monooxygenase from the valanimycin pathway that catalyzes the oxidation of isobutylamine to isobutylhydroxylamine. The last goal is to identify function of the other genes in the valanimycin cluster. The second metabolite to be investigated is the antitumor agent sparsomycin, a potent inhibitor of protein biosynthesis produced by S. sparsogenes. Sparsomycin is important because it inhibits the peptidyltranserase step in protein biosynthesis by interaction with 23S rRNA and because its biosynthesis involves novel biochemical reactions including the oxidative insertion of sulfur into a C-H bond, and the oxidative cleavage of both rings of the indole nucleus of tryptophan. Previous studies of sparsomycin revealed the outlines of the biosynthetic pathway and led to the isolation of a cosmid that confers sparsomycin resistance and carries the gene encoding an enzyme ("UCA synthase") involved in sparsomycin biosynthesis. Future studies of sparsomycin biosynthesis have several goals. The first is to sequence and characterize the gene(s) for sparsomycin self-resistance that reside on the isolated cosmic second is to localize and sequence the gene encoding UCA synthase. The third goal is to overproduce UCA synthase and carry out additional mechanistic studies with the enzyme. The fourth is to locate the genes encoding the proteins responsible for the oxidative insertion of sulfur and the oxidative opening of the indole nucleus. The final goal is to overproduce and study the sulfur insertion and dioxygenase proteins in vitro.
Funding Period: 1978-09-01 - 2003-11-30
more information: NIH RePORT

Top Publications

  1. ncbi Biochemical characterization of VlmL, a Seryl-tRNA synthetase encoded by the valanimycin biosynthetic gene cluster
    Ram P Garg
    Department of Chemistry, Rice University, Houston, Texas 77005, USA
    J Biol Chem 281:26785-91. 2006
  2. ncbi Biosynthetic investigations of lactonamycin and lactonamycin z: cloning of the biosynthetic gene clusters and discovery of an unusual starter unit
    Xiujun Zhang
    Department of Chemistry, MS60, Rice University, 6100 Main St, Houston, TX 77005, USA
    Antimicrob Agents Chemother 52:574-85. 2008
  3. ncbi Investigations of valanimycin biosynthesis: elucidation of the role of seryl-tRNA
    Ram P Garg
    Departments of Chemistry and Biochemistry and Cell Biology, Rice University, 6100 Main Street, Houston, TX 77005, USA
    Proc Natl Acad Sci U S A 105:6543-7. 2008
  4. ncbi Identification, characterization, and bioconversion of a new intermediate in valanimycin biosynthesis
    Ram P Garg
    Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005, USA
    J Am Chem Soc 131:9608-9. 2009
  5. ncbi Regulation of valanimycin biosynthesis in Streptomyces viridifaciens: characterization of VlmI as a Streptomyces antibiotic regulatory protein (SARP)
    Ram P Garg
    Department of Chemistry, Rice University, Houston, TX 77005, USA
    Microbiology 156:472-83. 2010

Detail Information

Publications5

  1. ncbi Biochemical characterization of VlmL, a Seryl-tRNA synthetase encoded by the valanimycin biosynthetic gene cluster
    Ram P Garg
    Department of Chemistry, Rice University, Houston, Texas 77005, USA
    J Biol Chem 281:26785-91. 2006
    ..Orthologs of VlmL were identified in two other actinomycetes species that also contain orthologs of the S. coelicolor SerRS. The significance of these findings is herein discussed...
  2. ncbi Biosynthetic investigations of lactonamycin and lactonamycin z: cloning of the biosynthetic gene clusters and discovery of an unusual starter unit
    Xiujun Zhang
    Department of Chemistry, MS60, Rice University, 6100 Main St, Houston, TX 77005, USA
    Antimicrob Agents Chemother 52:574-85. 2008
    ..Analysis of the gene clusters and of the precursor incorporation data suggested a hypothetical scheme for lactonamycinone biosynthesis...
  3. ncbi Investigations of valanimycin biosynthesis: elucidation of the role of seryl-tRNA
    Ram P Garg
    Departments of Chemistry and Biochemistry and Cell Biology, Rice University, 6100 Main Street, Houston, TX 77005, USA
    Proc Natl Acad Sci U S A 105:6543-7. 2008
    ..These findings provide an example of the involvement of an aminoacyl-tRNA in an antibiotic biosynthetic pathway...
  4. ncbi Identification, characterization, and bioconversion of a new intermediate in valanimycin biosynthesis
    Ram P Garg
    Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005, USA
    J Am Chem Soc 131:9608-9. 2009
    ..viridifaciens requires both the vlmJ and vlmK genes and that VlmJ catalyzes the ATP-dependent phosphorylation of the hydroxyl group of valanimycin hydrate prior to VlmK-catalyzed dehydration...
  5. ncbi Regulation of valanimycin biosynthesis in Streptomyces viridifaciens: characterization of VlmI as a Streptomyces antibiotic regulatory protein (SARP)
    Ram P Garg
    Department of Chemistry, Rice University, Houston, TX 77005, USA
    Microbiology 156:472-83. 2010
    ..Introduction of the same vlmI expression plasmid into an S. viridifaciens vlmI mutant restored valanimycin production to wild-type levels...