title: Expression and functional analysis of glutamate synthase small subunit-like proteins from archaeon Pyrococcus horikoshii.
abstract: Glutamate synthase, glutamine α-ketoglutarate amidotransferase (often abbreviated as GOGAT) is a key enzyme in the early stages of ammonia assimilation in bacteria, algae and plants, catalyzing the reductive transamidation of the amido nitrogen from glutamine to α-ketoglutarate to form two molecules of glutamate. Most bacterial glutamate synthases consist of a large and small subunit. The genomes of three Pyrococcus species harbour several open reading frames which show homology with the small subunit of glutamate synthase. There are no open reading frames which may be coding for a large subunit responsible for the glutamate formation in these pyrococcal genomes. In this work, two open reading frames PH0876 and PH1873 from P. horikoshii were cloned and expressed in Escherichia coli as soluble proteins. Both proteins show NADPH-dependent oxidoreductase activity using artificial electron acceptors iodonitrotetrazolium chloride at thermophilic conditions. It is possible that these open reading frames are the products of gene duplication and that they are the early forms of an electron transfer domain in archaea which may have later contributed to many electron transfer enzymes.
authors.affiliation: Department of Molecular Biology and Genetics, Faculty of Sciences and Letters, Istanbul Technical University Maslak, 34469 Istanbul, Turkey. dincturk@itu.edu.tr
authors.forename: H Benan
authors.initials: HB
authors.lastname: Dincturk
authors.forename: Raymond
authors.initials: R
authors.lastname: Cunin
authors.forename: Hande
authors.initials: H
authors.lastname: Akce
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D005970:Glutamate Synthase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D043902:Pyrococcus horikoshii / Q000737:chemistry / Q000145:classification / Q000201:enzymology* / Q000235:genetics
chemical_list: D019843:Archaeal Proteins; D021122:Protein Subunits; D005970:Glutamate Synthase