title: One-component styrene monooxygenases: an evolutionary view on a rare class of flavoproteins.
abstract: Styrene monooxygenases (SMOs) are catalysts for the enantioselective epoxidation of terminal alkenes. Most representatives comprise a reductase and a monooxygenase which are encoded by separate genes (styA, styB). Only six presumed self-sufficient one-component SMOs (styA2B) have previously been submitted to databases, and one has so far been characterized. StyA2B can be supported by another epoxidase (StyA1) encoded by styA1, a gene in direct neighborhood of styA2B. The present report describes the identification of a further styA1/styA2B-like SMO, which was detected in Rhodococcus opacus MR11. Based on the initially available sequences of styA2B-type SMOs, primers directed at conserved sequences were designed and a 7,012-bp genomic fragment from strain MR11 was obtained after PCRs and subsequent genome walking. Six open reading frames (ORFs) were detected and compared to genomic fragments of strains comprising either two- or one-component SMOs. Among the proteins encoded by the ORFs, the monooxygenase StyA1/StyA2B showed the highest divergence on amino acid level when comparing proteins from different sources. That finding, a rare distribution of styA2B genes among bacteria, and the general observation of evolution from simple to complex systems indicate that one-component SMOs evolved from two-component ancestors. Analysis of gene products from styA/styB- and styA1/styA2B-like SMOs revealed that a fusion of styA/styB to styA2B might have happened at least twice among microorganisms. This points to a convergent evolution of one-component SMOs.
authors.affiliation: Interdisciplinary Ecological Center, TU Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany. dirk-tischler@email.de
authors.forename: Dirk
authors.initials: D
authors.lastname: Tischler
authors.forename: Janosch A D
authors.initials: JA
authors.lastname: Gröning
authors.forename: Stefan R
authors.initials: SR
authors.lastname: Kaschabek
authors.forename: Michael
authors.initials: M
authors.lastname: Schlömann
mesh_terms: D000595:Amino Acid Sequence; D055162:Biocatalysis; D019143:Evolution, Molecular; D005420:Flavoproteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D023281:Genomics; D008969:Molecular Sequence Data; D010105:Oxygenases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012240:Rhodococcus / Q000201:enzymology / Q000235:genetics; D016415:Sequence Alignment; D013379:Substrate Specificity
chemical_list: D005420:Flavoproteins; D010105:Oxygenases; C026721:styrene monooxygenase