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Structure of Phenoxazinone synthase from Streptomyces antibioticus reveals a new type 2 copper center.
Structural highlights
FunctionPHSA_STRAT Could be involved in the spore pigmentation and melanin production. Catalyzes the oxidative coupling of 2-aminophenols to form the 2-aminophenoxazinone chromophore. 2-aminophenoxazinone synthesis proceeds via a sequence of three consecutive 2-electron aminophenol oxidations. First, the o-aminophenol is oxidized by two electrons to the quinone imine, which then conjugates to a second o-aminophenol molecule while still bound to the enzyme. This product is further oxidized by two electrons to give rise to the p-quinone imine. The last two steps of the reaction, another conjugation to generate the tricyclic structure and a final two-electron oxidation to yield the 2-aminophenoxazinone product, are thought to be non-enzymatic. It can also uuse 3-hydroxyanthranilic acid (HAA), 4-methyl-3-hydroxyanthranilic acid (MHA), 3,4-dihydroxy-L-phenylalanine (L-DOPA), ferrocyanide and thiophenol as substrates.[1] [2] [3] [4] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe multicopper oxidase phenoxazinone synthase (PHS) catalyzes the penultimate step in the biosynthesis of the antibiotic actinomycin D by Streptomyces antibioticus. PHS exists in two oligomeric forms: a dimeric form and a hexameric form, with older actinomycin-producing cultures containing predominately the hexameric form. The structure of hexameric PHS has been determined using X-ray diffraction to a resolution limit of 2.30 A and is found to contain several unexpected and distinctive features. The structure forms a hexameric ring that is centered on a pseudo 6-fold axis and has an outer diameter of 185 A with a large central cavity that has a diameter of 50 A. This hexameric structure is stabilized by a long loop connecting two domains; bound to this long loop is a fifth copper atom that is present as a type 2 copper. This copper atom is not present in any other multicopper oxidase, and its presence appears to stabilize the hexameric structure. Structure of phenoxazinone synthase from Streptomyces antibioticus reveals a new type 2 copper center.,Smith AW, Camara-Artigas A, Wang M, Allen JP, Francisco WA Biochemistry. 2006 Apr 11;45(14):4378-87. PMID:16584173[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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