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1h4j

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{{STRUCTURE_1h4j| PDB=1h4j | SCENE= }}
{{STRUCTURE_1h4j| PDB=1h4j | SCENE= }}
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'''METHYLOBACTERIUM EXTORQUENS METHANOL DEHYDROGENASE D303E MUTANT'''
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===METHYLOBACTERIUM EXTORQUENS METHANOL DEHYDROGENASE D303E MUTANT===
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==Overview==
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Two proteins specifically involved in methanol oxidation in the methylotrophic bacterium Methylobacterium extorquens have been modified by site-directed mutagenesis. Mutation of the proposed active site base (Asp303) to glutamate in methanol dehydrogenase (MDH) gave an active enzyme (D303E-MDH) with a greatly reduced affinity for substrate and with a lower activation energy. Results of kinetic and deuterium isotope studies showed that the essential mechanism in the mutant protein was unchanged, and that the step requiring activation by ammonia remained rate limiting. No spectrally detectable intermediates could be observed during the reaction. The X-ray structure, determined to 3 A resolution, of D303E-MDH showed that the position and coordination geometry of the Ca2+ ion in the active site was altered; the larger Glu303 side chain was coordinated to the Ca2+ ion and also hydrogen bonded to the O5 atom of pyrroloquinoline quinone (PQQ). The properties and structure of the D303E-MDH are consistent with the previous proposal that the reaction in MDH is initiated by proton abstraction involving Asp303, and that the mechanism involves a direct hydride transfer reaction. Mutation of the two adjacent cysteine residues that make up the novel disulfide ring in the active site of MDH led to an inactive enzyme, confirming the essential role of this remarkable ring structure. Mutations of cytochrome c(L), which is the electron acceptor from MDH was used to identify Met109 as the sixth ligand to the heme.
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(as it appears on PubMed at http://www.pubmed.gov), where 11502173 is the PubMed ID number.
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{{ABSTRACT_PUBMED_11502173}}
==About this Structure==
==About this Structure==
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[[Category: Dehydrogenase]]
[[Category: Dehydrogenase]]
[[Category: Quinoprotein]]
[[Category: Quinoprotein]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 06:36:43 2008''

Revision as of 03:36, 1 July 2008

Image:1h4j.png

Template:STRUCTURE 1h4j

METHYLOBACTERIUM EXTORQUENS METHANOL DEHYDROGENASE D303E MUTANT

Template:ABSTRACT PUBMED 11502173

About this Structure

1H4J is a Protein complex structure of sequences from Methylobacterium extorquens. Full crystallographic information is available from OCA.

Reference

Site-directed mutagenesis and X-ray crystallography of the PQQ-containing quinoprotein methanol dehydrogenase and its electron acceptor, cytochrome c(L)., Afolabi PR, Mohammed F, Amaratunga K, Majekodunmi O, Dales SL, Gill R, Thompson D, Cooper JB, Wood SP, Goodwin PM, Anthony C, Biochemistry. 2001 Aug 21;40(33):9799-809. PMID:11502173

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