The Escherichia coli Periplasmic Aldehyde Oxidoreductase Is an Exceptional Member of the Xanthine Oxidase Family of Molybdoenzymes

• DOI: 10.1021/acschembio.6b00572
• Publication Date: 2016-09-13T13:49:58Z
• Authors: Márcia A. S. Correia; Ana Rita Otrelo-C...; Viola Schwuchow; Kajsa G. V. Sigfr...; Michael Haumann; Maria João Romão; Silke Leimkühler; Teresa Santos-Silva
• Keywords: Molybdenum Cofactor

The xanthine oxidase (XO) family comprises molybdenum-dependent enzymes that usually form homodimers (or dimers of heterodimers/trimers) organized in three domains harbor two [2Fe-2S] clusters, one FAD, and a Mo cofactor. In this work, we crystallized an unusual member the family, periplasmic aldehyde oxidoreductase PaoABC from Escherichia coli. This is first example E. coli protein containing molybdopterin-cytosine-dinucleotide cofactor only heterotrimer XO so far structurally characterized. crystal structure revealed presence unexpected [4Fe-4S] cluster, anchored to additional 40 residues subdomain. According phylogenetic analysis, proteins cluster are widely spread many bacteria phyla, putatively through repeated gene transfer events. active site highly exposed surface with no aromatic arginine (PaoC-R440) making direct interaction PaoC-E692, which acts as base catalyst. order understand importance R440, kinetic assays were carried out, PaoC-R440H variant was also determined.