title: BlmB and TlmB provide resistance to the bleomycin family of antitumor antibiotics by N-acetylating metal-free bleomycin, tallysomycin, phleomycin, and zorbamycin.
abstract: The bleomycin (BLM) family of glycopeptide-derived antitumor antibiotics consists of BLMs, tallysomycins (TLMs), phleomycins (PLMs), and zorbamycin (ZBM). The self-resistant elements BlmB and TlmB, discovered from the BLM- and TLM-producing organisms Streptomyces verticillus ATCC15003 and Streptoalloteichus hindustanus E465-94 ATCC31158, respectively, are N-acetyltransferases that provide resistance to the producers by disrupting the metal-binding domain of the antibiotics required for activity. Although each member of the BLM family of antibiotics possesses a conserved metal-binding domain, the structural differences between each member, namely, the bithiazole moiety and C-terminal amine of BLMs, have been suggested to instill substrate specificity within BlmB. Here we report that BlmB and TlmB readily accept and acetylate BLMs, TLMs, PLMs, and ZBM in vitro but only in the metal-free forms. Kinetic analysis of BlmB and TlmB reveals there is no strong preference or rate enhancement for specific substrates, indicating that the structural differences between each member of the BLM family play a negligible role in substrate recognition, binding, or catalysis. Intriguingly, the zbm gene cluster from Streptomyces flavoviridis ATCC21892 does not contain an N-acetyltransferase, yet ZBM is readily acetylated by BlmB and TlmB. We subsequently established that S. flavoviridis lacks the homologue of BlmB and TlmB, and ZbmA, the ZBM-binding protein, alone is sufficient to provide ZBM resistance. We further confirmed that BlmB can indeed confer resistance to ZBM in vivo in S. flavoviridis, introduction of which into wild-type S. flavoviridis further increases the level of resistance.
authors.affiliation: Division of Pharmaceutical Sciences, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States.
authors.forename: Jane M
authors.initials: JM
authors.lastname: Coughlin
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Rudolf
authors.forename: Evelyn
authors.initials: E
authors.lastname: Wendt-Pienkowski
authors.forename: Liyan
authors.initials: L
authors.lastname: Wang
authors.forename: Claudia
authors.initials: C
authors.lastname: Unsin
authors.forename: Ute
authors.initials: U
authors.lastname: Galm
authors.forename: Dong
authors.initials: D
authors.lastname: Yang
authors.forename: Meifeng
authors.initials: M
authors.lastname: Tao
authors.forename: Ben
authors.initials: B
authors.lastname: Shen
mesh_terms: D000107:Acetylation; D000123:Acetyltransferases / Q000737:chemistry*; D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology; D001426:Bacterial Proteins / Q000737:chemistry*; D001761:Bleomycin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D013302:Streptomyces / Q000187:drug effects / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001761:Bleomycin; D000123:Acetyltransferases; C016126:talisomycin