2nvk

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[[Image:2nvk.gif|left|200px]]
[[Image:2nvk.gif|left|200px]]
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{{Structure
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<!--
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|PDB= 2nvk |SIZE=350|CAPTION= <scene name='initialview01'>2nvk</scene>, resolution 2.400&Aring;
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The line below this paragraph, containing "STRUCTURE_2nvk", creates the "Structure Box" on the page.
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|SITE=
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You may change the PDB parameter (which sets the PDB file loaded into the applet)
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|LIGAND= <scene name='pdbligand=FAD:FLAVIN-ADENINE+DINUCLEOTIDE'>FAD</scene>, <scene name='pdbligand=NAP:NADP+NICOTINAMIDE-ADENINE-DINUCLEOTIDE+PHOSPHATE'>NAP</scene>
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or the SCENE parameter (which sets the initial scene displayed when the page is loaded),
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|ACTIVITY= <span class='plainlinks'>[http://en.wikipedia.org/wiki/Thioredoxin-disulfide_reductase Thioredoxin-disulfide reductase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.8.1.9 1.8.1.9] </span>
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or leave the SCENE parameter empty for the default display.
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|GENE= Trxr-1 ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=7227 Drosophila melanogaster])
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|DOMAIN=
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{{STRUCTURE_2nvk| PDB=2nvk | SCENE= }}
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|RELATEDENTRY=
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|RESOURCES=<span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=2nvk FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2nvk OCA], [http://www.ebi.ac.uk/pdbsum/2nvk PDBsum], [http://www.rcsb.org/pdb/explore.do?structureId=2nvk RCSB]</span>
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}}
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'''Crystal Structure of Thioredoxin Reductase from Drosophila melanogaster'''
'''Crystal Structure of Thioredoxin Reductase from Drosophila melanogaster'''
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[[Category: Hondal, R J.]]
[[Category: Hondal, R J.]]
[[Category: Rould, M A.]]
[[Category: Rould, M A.]]
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[[Category: flavoprotein]]
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[[Category: Flavoprotein]]
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[[Category: oxidoreductase]]
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[[Category: Oxidoreductase]]
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[[Category: rossmann]]
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[[Category: Rossmann]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 09:57:34 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Mar 31 04:08:59 2008''
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Revision as of 06:57, 4 May 2008

Image:2nvk.gif


PDB ID 2nvk

Drag the structure with the mouse to rotate
2nvk, resolution 2.40Å ()
Ligands: ,
Gene: Trxr-1 (Drosophila melanogaster)
Activity: Thioredoxin-disulfide reductase, with EC number 1.8.1.9
Resources: FirstGlance, OCA, RCSB, PDBsum
Coordinates: save as pdb, mmCIF, xml



Crystal Structure of Thioredoxin Reductase from Drosophila melanogaster


Overview

Thioredoxin reductase (TR) from Drosophila melanogaster (DmTR) is a member of the glutathione reductase (GR) family of pyridine nucleotide disulfide oxidoreductases and catalyzes the reduction of the redox-active disulfide bond of thioredoxin. DmTR is notable for having high catalytic activity without the presence of a selenocysteine (Sec) residue (which is essential for the mammalian thioredoxin reductases). We report here the X-ray crystal structure of DmTR at 2.4 A resolution (Rwork = 19.8%, Rfree = 24.7%) in which the enzyme was truncated to remove the C-terminal tripeptide sequence Cys-Cys-Ser. We also demonstrate that tetrapeptides equivalent to the oxidized C-terminal active sites of both mouse mitochondrial TR (mTR3) and DmTR are substrates for the truncated forms of both enzymes. This truncated enzyme/peptide substrate system examines the kinetics of the ring-opening step that occurs during the enzymatic cycle of TR. The ring-opening step is 300-500-fold slower when Sec is replaced with Cys in mTR3 when using this system. Conversely, when Cys is replaced with Sec in DmTR, the rate of ring opening is only moderately increased (5-36-fold). Structures of these tetrapeptides were oriented in the active site of both enzymes using oxidized glutathione bound to GR as a template. DmTR has a more open tetrapeptide binding pocket than the mouse enzyme and accommodates the peptide Ser-Cys-Cys-Ser(ox) in a cis conformation that allows for the protonation of the leaving-group Cys by His464', which helps to explain why this TR can function without the need for Sec. In contrast, mTR3 shows a narrower pocket. One possible result of this narrower interface is that the mammalian redox-active tetrapeptide Gly-Cys-Sec-Gly may adopt a trans conformation for a better fit. This places the Sec residue farther away from the protonating histidine residue, but the lower pKa of Sec in comparison to that of Cys eliminates the need for Sec to be protonated.

About this Structure

2NVK is a Single protein structure of sequence from Drosophila melanogaster. Full crystallographic information is available from OCA.

Reference

Structural and biochemical studies reveal differences in the catalytic mechanisms of mammalian and Drosophila melanogaster thioredoxin reductases., Eckenroth BE, Rould MA, Hondal RJ, Everse SJ, Biochemistry. 2007 Apr 24;46(16):4694-705. Epub 2007 Mar 27. PMID:17385893 Page seeded by OCA on Sun May 4 09:57:34 2008

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