Crystal Structures of Cytochrome c<subscript>L</subscript> and Methanol Dehydrogenase from Hyphomicrobium denitrificans: Structural and Mechanistic Insights into Interactions between the Two Proteins.
In: Biochemistry, Jg. 45 (2006-03-21), Heft 11, S. 3481-3492
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Zugriff:
Methanol dehydrogenase (Hd-MDH) and its physiological electron acceptor, cytochrome CL (Hd-Cyt CL), isolated from a methylotrophic denitrifying bacterium, Hyphomicrobium denitrificans A3151, have been kinetically and structurally characterized; the X-ray structures of Hd-MDH and Hd-Cyt CL have been determined using molecular replacement at 2.5 and 2.0 Å resolution, respectively. To explain the mechanism for electron transfer between these proteins, the dependence of MDH activity on the concentration of Hd-Cyt CL has been investigated at pH 4.5–7.0. The Michaelis constant for Hd-Cyt CL shows the smallest value (∼0.3 μM) at pH 5.5. The pseudo-first-order rate constant (kobs) of the reduction of Hd-Cyt CL exhibits a hyperbolic concentration dependence of Hd-MDH at pH 5.5, although kobs linearly increases at pH 6.5. These findings indicate formation of a transient complex between these proteins during an electron transfer event. Hd-MDH (148 kDa) is a large tetrameric protein with an α2β2 subunit composition, showing a high degree of structural similarity with other MDHs. Hd-Cyt CL (19 kDa) exhibiting the α-band at 550.7 nm has a unique C-terminal region involving a disulfide bond between Cys47 and Cys165. Moreover, there is a pair of Hd-Cyt CL monomers related with a pseudo-2-fold axis of symmetry in the asymmetric unit, and the two monomers tightly interact with each other through three hydrogen bonds. This configuration is the first example in the studies of cytochrome C as the physiological electron acceptor for MDH. The docking simulation between the coupled Hd-Cyt CL molecules and the heterotetrameric Hd-MDH molecule has been carried out. [ABSTRACT FROM AUTHOR]
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Crystal Structures of Cytochrome c<subscript>L</subscript> and Methanol Dehydrogenase from Hyphomicrobium denitrificans: Structural and Mechanistic Insights into Interactions between the Two Proteins.
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Autor/in / Beteiligte Person: | Nojiri, Masaki ; Hira, Daisuke ; Yamaguchi, Kazuya ; Okajima, Toshihide ; Tanizawa, Katsuyuki ; Suzuki, Shinnichiro |
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Zeitschrift: | Biochemistry, Jg. 45 (2006-03-21), Heft 11, S. 3481-3492 |
Veröffentlichung: | 2006 |
Medientyp: | academicJournal |
ISSN: | 0006-2960 (print) |
DOI: | 10.1021/bi051877j |
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