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2oo5

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[[Image:2oo5.gif|left|200px]]
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{{STRUCTURE_2oo5| PDB=2oo5 | SCENE= }}
{{STRUCTURE_2oo5| PDB=2oo5 | SCENE= }}
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'''Structure of transhydrogenase (dI.H2NADH)2(dIII.NADP+)1 asymmetric complex'''
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===Structure of transhydrogenase (dI.H2NADH)2(dIII.NADP+)1 asymmetric complex===
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==Overview==
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Transhydrogenase couples the redox reaction between NADH and NADP+ to proton translocation across a membrane. The enzyme comprises three components; dI binds NAD(H), dIII binds NADP(H), and dII spans the membrane. The 1,4,5,6-tetrahydro analogue of NADH (designated H2NADH) bound to isolated dI from Rhodospirillum rubrum transhydrogenase with similar affinity to the physiological nucleotide. Binding of either NADH or H2NADH led to closure of the dI mobile loop. The 1,4,5,6-tetrahydro analogue of NADPH (H2NADPH) bound very tightly to isolated R. rubrum dIII, but the rate constant for dissociation was greater than that for NADPH. The replacement of NADP+ on dIII either with H2NADPH or with NADPH caused a similar set of chemical shift alterations, signifying an equivalent conformational change. Despite similar binding properties to the natural nucleotides, neither H2NADH nor H2NADPH could serve as a hydride donor in transhydrogenation reactions. Mixtures of dI and dIII form dI2dIII1 complexes. The nucleotide charge distribution of complexes loaded either with H2NADH and NADP+ or with NAD+ and H2NADPH should more closely mimic the ground states for forward and reverse hydride transfer, respectively, than previously studied dead-end species. Crystal structures of such complexes at 2.6 and 2.3 A resolution are described. A transition state for hydride transfer between dihydronicotinamide and nicotinamide derivatives determined in ab initio quantum mechanical calculations resembles the organization of nucleotides in the transhydrogenase active site in the crystal structure. Molecular dynamics simulations of the enzyme indicate that the (dihydro)nicotinamide rings remain close to a ground state for hydride transfer throughout a 1.4 ns trajectory.
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(as it appears on PubMed at http://www.pubmed.gov), where 17323922 is the PubMed ID number.
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{{ABSTRACT_PUBMED_17323922}}
==About this Structure==
==About this Structure==
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[[Category: Jackson, J B.]]
[[Category: Jackson, J B.]]
[[Category: Rossmann fold]]
[[Category: Rossmann fold]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 11:18:29 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 16:33:04 2008''

Revision as of 13:33, 28 July 2008

Image:2oo5.png

Template:STRUCTURE 2oo5

Structure of transhydrogenase (dI.H2NADH)2(dIII.NADP+)1 asymmetric complex

Template:ABSTRACT PUBMED 17323922

About this Structure

2OO5 is a Protein complex structure of sequences from Rhodospirillum rubrum. Full crystallographic information is available from OCA.

Reference

Structures of the dI2dIII1 complex of proton-translocating transhydrogenase with bound, inactive analogues of NADH and NADPH reveal active site geometries., Bhakta T, Whitehead SJ, Snaith JS, Dafforn TR, Wilkie J, Rajesh S, White SA, Jackson JB, Biochemistry. 2007 Mar 20;46(11):3304-18. Epub 2007 Feb 27. PMID:17323922

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