title: Adenylate-forming enzymes of rubradirin biosynthesis: RubC1 is a bifunctional enzyme with aminocoumarin acyl ligase and tyrosine-activating domains.
abstract: The biosynthesis of aminocoumarin antibiotics requires two acyladenylate-forming enzymes: one for the activation of L-tyrosine as a precursor of the aminocoumarin moiety and another for the linkage of an acyl moiety to the aminocoumarin moiety. Unexpectedly, the biosynthetic gene cluster of the aminocoumarin antibiotic rubradirin was found to contain three genes for putative acyladenylate-forming enzymes of aminocoumarin biosynthesis and conjugation. We expressed, purified, and investigated these three proteins. Orf4 (55 kDa) was shown to be an active aminocoumarin acyl ligase. RubF6 (56 kDa) was inactive, but could be converted into an active enzyme by site-directed mutagenesis. RubC1 (138 kDa) was shown to be a unique bifunctional enzyme, comprising an aminocoumarin acyl ligase, and tyrosine-adenylation and peptidyl-carrier domains. This natural hybrid enzyme is unique among known proteins. A hypothesis is proposed as to how such an enzyme could offer a particularly effective machinery for aminocoumarin antibiotic biosynthesis.
authors: Pharmazeutisches Institut, Universität Tübingen, Germany.
authors: Björn
authors: B
authors: Boll
authors: Susanne
authors: S
authors: Hennig
authors: Chunsong
authors: C
authors: Xie
authors: Jae Kyong
authors: JK
authors: Sohng
authors: Lutz
authors: L
authors: Heide
mesh_terms: D000595:Amino Acid Sequence; D049933:Aminocoumarins / Q000378:metabolism*; D055162:Biocatalysis; D004789:Enzyme Activation; D008025:Ligases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009285:Naphthoquinones / Q000378:metabolism; D016366:Open Reading Frames; D013302:Streptomyces / Q000201:enzymology*; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D049933:Aminocoumarins; D009285:Naphthoquinones; D014443:Tyrosine; C002857:rubradirin; D008025:Ligases