title: Identification of an unusual type II thioesterase in the dithiolopyrrolone antibiotics biosynthetic pathway.
abstract: Dithiolopyrrolone group antibiotics characterized by an electronically unique dithiolopyrrolone heterobicyclic core are known for their antibacterial, antifungal, insecticidal and antitumor activities. Recently the biosynthetic gene clusters for two dithiolopyrrolone compounds, holomycin and thiomarinol, have been identified respectively in different bacterial species. Here, we report a novel dithiolopyrrolone biosynthetic gene cluster (aut) isolated from Streptomyces thioluteus DSM 40027 which produces two pyrrothine derivatives, aureothricin and thiolutin. By comparison with other characterized dithiolopyrrolone clusters, eight genes in the aut cluster were verified to be responsible for the assembly of dithiolopyrrolone core. The aut cluster was further confirmed by heterologous expression and in-frame gene deletion experiments. Intriguingly, we found that the heterogenetic thioesterase HlmK derived from the holomycin (hlm) gene cluster in Streptomyces clavuligerus significantly improved heterologous biosynthesis of dithiolopyrrolones in Streptomyces albus through coexpression with the aut cluster. In the previous studies, HlmK was considered invalid because it has a Ser to Gly point mutation within the canonical Ser-His-Asp catalytic triad of thioesterases. However, gene inactivation and complementation experiments in our study unequivocally demonstrated that HlmK is an active distinctive type II thioesterase that plays a beneficial role in dithiolopyrrolone biosynthesis.
authors.affiliation: National Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhai
authors.affiliation: National Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Silei
authors.initials: S
authors.lastname: Bai
authors.affiliation: National Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Liu
authors.affiliation: National Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Liyuan
authors.initials: L
authors.lastname: Yang
authors.affiliation: Institute of Microbial Pharmaceuticals, College of Life and Health Sciences, Northeastern University, Shenyang 110819, China.
authors.forename: Li
authors.initials: L
authors.lastname: Han
authors.affiliation: Institute of Microbial Pharmaceuticals, College of Life and Health Sciences, Northeastern University, Shenyang 110819, China.
authors.forename: Xueshi
authors.initials: X
authors.lastname: Huang
authors.affiliation: National Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China. Electronic address: hejingjj@mail.hzau.edu.cn.
authors.forename: Jing
authors.initials: J
authors.lastname: He
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D053898:Biosynthetic Pathways; D020134:Catalytic Domain; D003001:Cloning, Molecular; D019295:Computational Biology; D004950:Esterases / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005810:Multigene Family; D010802:Phylogeny; D011758:Pyrroles / Q000737:chemistry*; D013302:Streptomyces / Q000201:enzymology* / Q000235:genetics; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013869:Thiolester Hydrolases / Q000096:biosynthesis* / Q000737:chemistry
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D011758:Pyrroles; D013438:Sulfhydryl Compounds; C010684:aureothricin; D004950:Esterases; D013869:Thiolester Hydrolases
keywords: Aureothricin; Biosynthetic gene cluster; Dithiolopyrrolone; Heterologous expression; In-frame gene deletion; Type II thioesterase