title: Asm8, a specific LAL-type activator of 3-amino-5-hydroxybenzoate biosynthesis in ansamitocin production.
abstract: The highly potent antitumor agent ansamitocin P3 is a macrolactam isolated from Actinosynnema pretiosum ATCC 31565. A 120-kb DNA fragment was previously identified as the ansamitocin biosynthetic gene cluster, and contains genes for polyketide assembly, precursor synthesis, post-polyketide synthesis modification, and regulation. Within the biosynthetic gene cluster, asm8 encodes an 1117-amino-acid protein with a high degree of similarity to the large ATP-binding LuxR family-type regulators. In the current study, we determined that inactivation of asm8 by gene replacement in ATCC 31565 resulted in the complete loss of ansamitocin production, and that complementation with a cloned asm8 gene restored ansamitocin biosynthesis. Interestingly, the disruption of asm8 decreased the transcription of genes responsible for 3-amino-5-hydroxybenzoate (AHBA) formation, the starter unit required for ansamitocin biosynthesis. Subsequently, feeding of exogenous AHBA to the asm8 mutant restored ansamitocin biosynthesis, which showed that Asm8 is a specific positive regulator in AHBA biosynthesis. In addition, investigation of asm8 homologs identified two new ansamitocin producers, and inactivation of the asm8 homolog in A. pretiosum ATCC 31280 abolished ansamitocin production in this strain. Characterization of the positive regulator Asm8 and discovery of the two new ansamitocin producers paves the way for further improving production of this important antitumor agent.
authors.affiliation: State Key Laboratory of Microbial Metabolism and School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Wenqin
authors.initials: W
authors.lastname: Pan
authors.forename: Qianjin
authors.initials: Q
authors.lastname: Kang
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Linquan
authors.initials: L
authors.lastname: Bai
authors.forename: Zixin
authors.initials: Z
authors.lastname: Deng
mesh_terms: D000192:Actinomycetales / Q000235:genetics* / Q000378:metabolism; D062365:Aminobenzoates / Q000737:chemistry; D000970:Antineoplastic Agents / Q000737:chemistry*; D005285:Fermentation; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D062385:Hydroxybenzoates / Q000737:chemistry; D008453:Maytansine / Q000031:analogs & derivatives* / Q000096:biosynthesis; D005810:Multigene Family; D010957:Plasmids / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D062365:Aminobenzoates; D000970:Antineoplastic Agents; D062385:Hydroxybenzoates; D012097:Repressor Proteins; D015534:Trans-Activators; C064778:LuxR autoinducer binding proteins; D008453:Maytansine; C015682:ansamitocins; C031509:3-amino-5-hydroxybenzoic acid