title: C-S bond cleavage by a polyketide synthase domain.
abstract: Leinamycin (LNM) is a sulfur-containing antitumor antibiotic featuring an unusual 1,3-dioxo-1,2-dithiolane moiety that is spiro-fused to a thiazole-containing 18-membered lactam ring. The 1,3-dioxo-1,2-dithiolane moiety is essential for LNM's antitumor activity, by virtue of its ability to generate an episulfonium ion intermediate capable of alkylating DNA. We have previously cloned and sequenced the lnm gene cluster from Streptomyces atroolivaceus S-140. In vivo and in vitro characterizations of the LNM biosynthetic machinery have since established that: (i) the 18-membered macrolactam backbone is synthesized by LnmP, LnmQ, LnmJ, LnmI, and LnmG, (ii) the alkyl branch at C-3 of LNM is installed by LnmK, LnmL, LnmM, and LnmF, and (iii) leinamycin E1 (LNM E1), bearing a thiol moiety at C-3, is the nascent product of the LNM hybrid nonribosomal peptide synthetase (NRPS)-acyltransferase (AT)-less type I polyketide synthase (PKS). Sulfur incorporation at C-3 of LNM E1, however, has not been addressed. Here we report that: (i) the bioinformatics analysis reveals a pyridoxal phosphate (PLP)-dependent domain, we termed cysteine lyase (SH) domain (LnmJ-SH), within PKS module-8 of LnmJ; (ii) the LnmJ-SH domain catalyzes C-S bond cleavage by using l-cysteine and l-cysteine S-modified analogs as substrates through a PLP-dependent β-elimination reaction, establishing l-cysteine as the origin of sulfur at C-3 of LNM; and (iii) the LnmJ-SH domain, sharing no sequence homology with any other enzymes catalyzing C-S bond cleavage, represents a new family of PKS domains that expands the chemistry and enzymology of PKSs and might be exploited to incorporate sulfur into polyketide natural products by PKS engineering.
authors.affiliation: Department of Chemistry, The Scripps Research Institute, Jupiter, FL 33458;
authors.forename: Ming
authors.initials: M
authors.lastname: Ma
authors.affiliation: Department of Chemistry, The Scripps Research Institute, Jupiter, FL 33458;
authors.forename: Jeremy R
authors.initials: JR
authors.lastname: Lohman
authors.affiliation: Division of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, WI 53705;
authors.forename: Tao
authors.initials: T
authors.lastname: Liu
authors.affiliation: Department of Chemistry, The Scripps Research Institute, Jupiter, FL 33458; Division of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, WI 53705; Department of Molecular Therapeutics, The Scripps Research Institute, Jupiter, FL 33458; Natural Products Library Initiative at The Scripps Research Institute, The Scripps Research Institute, Jupiter, FL 33458 shenb@scripps.edu.
authors.forename: Ben
authors.initials: B
authors.lastname: Shen
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry*; D013437:Carbon-Sulfur Lyases / Q000737:chemistry; D019295:Computational Biology; D003545:Cysteine / Q000737:chemistry; D015195:Drug Design; D007769:Lactams / Q000737:chemistry; D018942:Macrolides / Q000737:chemistry; D005810:Multigene Family; D010802:Phylogeny; D048630:Polyketide Synthases / Q000737:chemistry*; D061065:Polyketides / Q000737:chemistry; D015202:Protein Engineering / Q000379:methods; D017434:Protein Structure, Tertiary; D013302:Streptomyces / Q000378:metabolism; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds; D013440:Sulfides / Q000737:chemistry*; D013844:Thiazoles / Q000737:chemistry; D013871:Thiones / Q000737:chemistry
chemical_list: D000903:Antibiotics, Antineoplastic; D007769:Lactams; D018942:Macrolides; D061065:Polyketides; D013438:Sulfhydryl Compounds; D013440:Sulfides; D013844:Thiazoles; D013871:Thiones; C059000:leinamycin; D002244:Carbon; D048630:Polyketide Synthases; D013437:Carbon-Sulfur Lyases; C019971:cysteine lyase; D003545:Cysteine
keywords: cysteine metabolism; enzyme mechanism; genome mining; pathway engineering; sulfur metabolism