1. The Crystal Structure of the Apoenzyme of the Iron–Sulphur Cluster-free Hydrogenase
- Author
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Pilak, Oliver, Mamat, Björn, Vogt, Sonja, Hagemeier, Christoph H., Thauer, Rudolf K., Shima, Seigo, Vonrhein, Clemens, Warkentin, Eberhard, and Ermler, Ulrich
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CRYSTALS , *CHEMICAL structure , *HYDROGENASE , *ARCHAEBACTERIA - Abstract
The iron–sulphur cluster-free hydrogenase (Hmd, EC 1.12.98.2) from methanogenic archaea is a novel type of hydrogenase that tightly binds an iron-containing cofactor. The iron is coordinated by two CO molecules, one sulphur and a pyridone derivative, which is linked via a phosphodiester bond to a guanosine base. We report here on the crystal structure of the Hmd apoenzyme from Methanocaldococcus jannaschii at 1.75Å and from Methanopyrus kandleri at 2.4Å resolution. Homodimeric Hmd reveals a unique architecture composed of one central and two identical peripheral globular units. The central unit is composed of the intertwined C-terminal segments of both subunits, forming a novel intersubunit fold. The two peripheral units consist of the N-terminal domain of each subunit. The Rossmann fold-like structure of the N-terminal domain contains a mononucleotide-binding site, which could harbour the GMP moiety of the cofactor. Another binding site for the iron-containing cofactor is most probably Cys176, which is located at the bottom of a deep intersubunit cleft and which has been shown to be essential for enzyme activity. Adjacent to the iron of the cofactor modelled as a ligand to Cys176, an extended U-shaped extra electron density, interpreted as a polyethyleneglycol fragment, suggests a binding site for the substrate methenyltetrahydromethanopterin. [Copyright &y& Elsevier]
- Published
- 2006
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