title: Succinate complex crystal structures of the alpha-ketoglutarate-dependent dioxygenase AtsK: steric aspects of enzyme self-hydroxylation.
abstract: The alkylsulfatase AtsK from Pseudomonas putida S-313 is a member of the non-heme iron(II)-alpha-ketoglutarate-dependent dioxygenase superfamily. In the initial step of their catalytic cycle, enzymes belonging to this widespread and versatile family coordinate molecular oxygen to the iron center in the active site. The subsequent decarboxylation of the cosubstrate alpha-ketoglutarate yields carbon dioxide, succinate, and a highly reactive ferryl (IV) species, which is required for substrate oxidation via a complex mechanism involving the transfer of radical species. Non-productive activation of oxygen may lead to harmful side reactions; therefore, such enzymes need an effective built-in protection mechanism. One of the ways of controlling undesired side reactions is the self-hydroxylation of an aromatic side chain, which leads to an irreversibly inactivated species. Here we describe the crystal structure of the alkylsulfatase AtsK in complexes with succinate and with Fe(II)/succinate. In the crystal structure of the AtsK-Fe(II)-succinate complex, the side chain of Tyr(168) is co-ordinated to the iron, suggesting that Tyr(168) is the target of enzyme self-hydroxylation. This is the first structural study of an Fe(II)-alpha-ketoglutarate-dependent dioxygenase that presents an aromatic side chain coordinated to the metal center, thus allowing structural insight into this protective mechanism of enzyme self-inactivation.
authors.affiliation: Lehrstuhl für Strukturchemie, Universität Göttingen, Tammannstrasse 4, D-37077 Göttingen, Germany.
authors.forename: Ilka
authors.initials: I
authors.lastname: Müller
authors.forename: Claudia
authors.initials: C
authors.lastname: Stückl
authors.forename: James
authors.initials: J
authors.lastname: Wakeley
authors.forename: Michael
authors.initials: M
authors.lastname: Kertesz
authors.forename: Isabel
authors.initials: I
authors.lastname: Usón
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D049308:Dioxygenases / Q000737:chemistry* / Q000378:metabolism*; D006900:Hydroxylation; D007501:Iron / Q000737:chemistry / Q000378:metabolism; D007656:Ketoglutaric Acids / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D016958:Pseudomonas putida / Q000201:enzymology*; D019802:Succinic Acid / Q000737:chemistry / Q000378:metabolism*; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D007656:Ketoglutaric Acids; D014443:Tyrosine; D019802:Succinic Acid; D007501:Iron; D049308:Dioxygenases; D010100:Oxygen