title: Structure of the non-redox-active tungsten/[4Fe:4S] enzyme acetylene hydratase.
abstract: The tungsten-iron-sulfur enzyme acetylene hydratase stands out from its class because it catalyzes a nonredox reaction, the hydration of acetylene to acetaldehyde. Sequence comparisons group the protein into the dimethyl sulfoxide reductase family, and it contains a bis-molybdopterin guanine dinucleotide-ligated tungsten atom and a cubane-type [4Fe:4S] cluster. The crystal structure of acetylene hydratase at 1.26 A now shows that the tungsten center binds a water molecule that is activated by an adjacent aspartate residue, enabling it to attack acetylene bound in a distinct, hydrophobic pocket. This mechanism requires a strong shift of pK(a) of the aspartate, caused by a nearby low-potential [4Fe:4S] cluster. To access this previously unrecognized W-Asp active site, the protein evolved a new substrate channel distant from where it is found in other molybdenum and tungsten enzymes.
authors.affiliation: Fachbereich Biologie, Universität Konstanz, 78457 Konstanz, Germany.
authors.forename: Grazyna B
authors.initials: GB
authors.lastname: Seiffert
authors.forename: G Matthias
authors.initials: GM
authors.lastname: Ullmann
authors.forename: Albrecht
authors.initials: A
authors.lastname: Messerschmidt
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schink
authors.forename: Peter M H
authors.initials: PM
authors.lastname: Kroneck
authors.forename: Oliver
authors.initials: O
authors.lastname: Einsle
mesh_terms: D001665:Binding Sites / Q000235:genetics; D003460:Crystallization; D020564:Deltaproteobacteria / Q000737:chemistry*; D006836:Hydro-Lyases / Q000737:chemistry*; D008958:Models, Molecular; D055672:Static Electricity; D014414:Tungsten / Q000737:chemistry
chemical_list: D006836:Hydro-Lyases; C096200:acetylene hydratase; D014414:Tungsten