tailieunhanh - Báo cáo khoa học: A periplasmic aldehyde oxidoreductase represents the first molybdopterin cytosine dinucleotide cofactor containing molybdo-flavoenzyme from Escherichia coli

Three DNA regions carrying genes encoding putative homologs of xanthine dehydrogenases were identified inEscherichia coli, named xdhABC, xdhD, andyagTSRQ. Here, we describe the purification and characterization of gene products of the yagTSRQ operon, a molybdenum-containing iron– sulfur flavoprotein from E. coli, which is located in the periplasm. | A periplasmic aldehyde oxidoreductase represents the first molybdopterin cytosine dinucleotide cofactor containing molybdo-flavoenzyme from Escherichia coli Meina Neumann1 Gerd Mittelstadt1 Chantal lobbi-Nivol2 Miguel Saggu3 Friedhelm Lendzian3 Peter Hildebrandt3 and Silke Leimkuhler1 1 Institute of Biochemistry and Biology University of Potsdam Germany 2 Laboratoire de Chimie Bacterienne IFR 88 Institut Biologie Structurale et Microbiologie CNRS Marseille France 3 Max-Volmer-Laboratories Institut fur Chemie Technische Universitat Berlin Germany Keywords aldehyde oxidoreductase aromatic aldehyde MCD molybdenum molybdo-flavoenzyme Correspondence S. Leimkuhler Institute of Biochemistry and Biology University of Potsdam D-14476 Potsdam Germany Fax 49 331 977 5128 Tel 49 331 977 5603 E-mail sleim@ Received 2 February 2009 revised 10 March 2009 accepted 11 March 2009 doi Three DNA regions carrying genes encoding putative homologs of xanthine dehydrogenases were identified in Escherichia coli named xdhABC xdhD and yagTSRQ. Here we describe the purification and characterization of gene products of the yagTSRQ operon a molybdenum-containing ironsulfur flavoprotein from E. coli which is located in the periplasm. The 135 kDa enzyme comprised a noncovalent abc heterotrimer with a large kDa molybdenum cofactor Moco -containing YagR subunit a medium kDa FAD-containing YagS subunit and a small kDa 2 X 2Fe2S -containing YagT subunit. YagQ is not a subunit of the mature enzyme and the protein is expected to be involved in Moco modification and insertion into YagTSR. Analysis of the form of Moco present in YagTSR revealed the presence of the molybdopterin cytosine dinucleotide cofactor. Two different 2Fe2S clusters typical for this class of enzyme were identified by EPR. YagTSR represents the first example of a molyb-dopterin cytosine dinucleotide-containing protein in E. coli. Kinetic characterization of the enzyme .