title: Module fusion in an A-type flavoprotein from the cyanobacterium Synechocystis condenses a multiple-component pathway in a single polypeptide chain.
abstract: The A-type flavoproteins (ATF) are modular proteins involved in multi-component electron transfer pathways, having oxygen reductase activity. They are complex flavoproteins containing two distinct structural domains, one having an FMN in a flavodoxin-like fold and the other a binuclear iron centre within a metallo-beta-lactamase-like fold. Here, we report the purification and characterisation of a recombinant ATF from the cyanobacterium Synechoystis sp. PCC 6803, which has the unique feature of comprising an additional third domain with similarities towards flavin:NAD(P)H reductases. The latter was expressed independently as a truncated protein form and found to be capable of receiving electrons from NADH as well as to indiscriminately bind either one FAD or one FMN with equivalent affinities. Further kinetic studies have shown that the intact ATF is an NADH:oxygen oxidoreductase, with the catalytic ability to fully reduce oxygen to water. Thus, this constitutes an example on how structural modules found within partner proteins from an electron transfer pathway can be combined in a single polypeptide chain achieving identical catalytic activities.
authors.affiliation: Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Rua da Quinta Grande 6, Apt 127, 2780-156 Oeiras, Portugal.
authors.forename: João B
authors.initials: JB
authors.lastname: Vicente
authors.forename: Cláudio M
authors.initials: CM
authors.lastname: Gomes
authors.forename: Alain
authors.initials: A
authors.lastname: Wasserfallen
authors.forename: Miguel
authors.initials: M
authors.lastname: Teixeira
mesh_terms: D000595:Amino Acid Sequence; D000458:Cyanobacteria / Q000378:metabolism*; D004579:Electron Transport; D005486:Flavin Mononucleotide / Q000378:metabolism; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D005420:Flavoproteins / Q000378:metabolism*; D007700:Kinetics; D008956:Models, Chemical; D008969:Molecular Sequence Data; D016415:Sequence Alignment
chemical_list: D005420:Flavoproteins; D005182:Flavin-Adenine Dinucleotide; D005486:Flavin Mononucleotide