Structure of the non-redox-active tungsten/[4Fe:4S] enzyme acetylene hydratase |
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Authors: | Seiffert Grazyna B Ullmann G Matthias Messerschmidt Albrecht Schink Bernhard Kroneck Peter M H Einsle Oliver |
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Institution: | Fachbereich Biologie, Universit?t Konstanz, 78457 Konstanz, Germany. |
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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. |
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