title: Structure of Hordeum vulgare NADPH-dependent thioredoxin reductase 2. Unwinding the reaction mechanism.
abstract: Thioredoxins (Trxs) are protein disulfide reductases that regulate the intracellular redox environment and are important for seed germination in plants. Trxs are in turn regulated by NADPH-dependent thioredoxin reductases (NTRs), which provide reducing equivalents to Trx using NADPH to recycle Trxs to the active form. Here, the first crystal structure of a cereal NTR, HvNTR2 from Hordeum vulgare (barley), is presented, which is also the first structure of a monocot plant NTR. The structure was determined at 2.6 A resolution and refined to an R(cryst) of 19.0% and an R(free) of 23.8%. The dimeric protein is structurally similar to the structures of AtNTR-B from Arabidopsis thaliana and other known low-molecular-weight NTRs. However, the relative position of the two NTR cofactor-binding domains, the FAD and the NADPH domains, is not the same. The NADPH domain is rotated by 25 degrees and bent by a 38% closure relative to the FAD domain in comparison with AtNTR-B. The structure may represent an intermediate between the two conformations described previously: the flavin-oxidizing (FO) and the flavin-reducing (FR) conformations. Here, analysis of interdomain contacts as well as phylogenetic studies lead to the proposal of a new reaction scheme in which NTR-Trx interactions mediate the FO to FR transformation.
authors.affiliation: Carlsberg Laboratory, Denmark.
authors.forename: Kristine G
authors.initials: KG
authors.lastname: Kirkensgaard
authors.forename: Per
authors.initials: P
authors.lastname: Hägglund
authors.forename: Christine
authors.initials: C
authors.lastname: Finnie
authors.forename: Birte
authors.initials: B
authors.lastname: Svensson
authors.forename: Anette
authors.initials: A
authors.lastname: Henriksen
mesh_terms: D000494:Allosteric Regulation; D000495:Allosteric Site; D017360:Arabidopsis / Q000201:enzymology; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray; D038181:FMN Reductase / Q000737:chemistry / Q000378:metabolism; D018525:Germination; D001467:Hordeum / Q000201:enzymology; D010084:Oxidation-Reduction; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D040681:Structural Homology, Protein; D054482:Thioredoxin Reductase 2 / Q000737:chemistry* / Q000378:metabolism; D013880:Thioredoxin-Disulfide Reductase / Q000737:chemistry* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D038181:FMN Reductase; C497522:NTRB protein, Arabidopsis; D054482:Thioredoxin Reductase 2; D013880:Thioredoxin-Disulfide Reductase
references.citation: Acta Crystallogr D Biol Crystallogr. 2005 Dec;61(Pt 12):1603-11
references.pmid: 16301794
references.citation: J Biol Chem. 2004 Oct 15;279(42):43821-7
references.pmid: 15292215
references.citation: Planta. 2003 Jul;217(3):392-9
references.pmid: 14520565
references.citation: Acta Crystallogr D Biol Crystallogr. 2002 Nov;58(Pt 11):1948-54
references.pmid: 12393927
references.citation: Plant Physiol Biochem. 2004 Apr;42(4):265-71
references.pmid: 15120110
references.citation: J Biol Chem. 1964 Oct;239:3445-52
references.pmid: 14245401
references.citation: J Mol Biol. 1988 Dec 20;204(4):1019-29
references.pmid: 3221397
references.citation: FEBS Lett. 2003 Dec 18;555(3):443-8
references.pmid: 14675753
references.citation: J Proteome Res. 2008 Dec;7(12):5270-6
references.pmid: 19367707
references.citation: Acta Crystallogr D Biol Crystallogr. 2006 Apr;62(Pt 4):439-50
references.pmid: 16552146
references.citation: Protoplasma. 2009 Mar;235(1-4):3-15
references.pmid: 19219525
references.citation: Biochemistry. 2008 Sep 16;47(37):9728-37
references.pmid: 18717593
references.citation: Acta Crystallogr D Biol Crystallogr. 2000 Dec;56(Pt 12):1622-4
references.pmid: 11092928
references.citation: Eur J Biochem. 2000 Oct;267(20):6110-7
references.pmid: 11012662
references.citation: Biochemistry. 1988 Apr 5;27(7):2300-5
references.pmid: 2898258
references.citation: Eur J Biochem. 2003 Jun;270(12):2633-43
references.pmid: 12787030
references.citation: Planta. 1998 May;205(1):12-22
references.pmid: 9599802
references.citation: FEBS Lett. 1979 Nov 1;107(1):141-5
references.pmid: 227737
references.citation: Plant Cell Physiol. 2004 Apr;45(4):407-15
references.pmid: 15111715
references.citation: Acta Crystallogr D Biol Crystallogr. 2007 Jul;63(Pt 7):833-43
references.pmid: 17582174
references.citation: Nature. 1991 Jul 11;352(6331):172-4
references.pmid: 2067578
references.citation: Biochemistry. 1997 Aug 5;36(31):9464-77
references.pmid: 9235991
references.citation: Acta Crystallogr D Biol Crystallogr. 1997 May 1;53(Pt 3):240-55
references.pmid: 15299926
references.citation: Nucleic Acids Res. 2007 Jul;35(Web Server issue):W375-83
references.pmid: 17452350
references.citation: Bioinformatics. 1999 Apr;15(4):305-8
references.pmid: 10320398
references.citation: J Mol Biol. 1994 Feb 25;236(3):800-16
references.pmid: 8114095
references.citation: J Mol Biol. 1996 Dec 20;264(5):1044-57
references.pmid: 9000629
references.citation: J Biol Chem. 1964 Oct;239:3436-44
references.pmid: 14245400
references.citation: Biochim Biophys Acta. 2009 Jan;1794(1):124-8
references.pmid: 18930846
references.citation: Proc Natl Acad Sci U S A. 1995 Jun 6;92(12):5620-4
references.pmid: 7777559
references.citation: J Biol Chem. 1986 Nov 15;261(32):14997-5005
references.pmid: 3533930
references.citation: Plant Physiol. 2008 Feb;146(2):789-99
references.pmid: 18162587
references.citation: Acta Crystallogr D Biol Crystallogr. 2004 Dec;60(Pt 12 Pt 1):2126-32
references.pmid: 15572765
references.citation: Protein Eng. 1995 Feb;8(2):127-34
references.pmid: 7630882
references.citation: Science. 2000 Aug 18;289(5482):1190-4
references.pmid: 10947986
references.citation: Biochem J. 2000 Feb 15;346 Pt 1:1-8
references.pmid: 10657232
references.citation: Biochim Biophys Acta. 2009 Mar;1794(3):554-62
references.pmid: 19110078
references.citation: J Mol Graph Model. 2002 Dec;21(3):181-3
references.pmid: 12463636
references.citation: J Mol Biol. 1994 Jan 28;235(4):1357-63
references.pmid: 8308900
references.citation: J Exp Bot. 2007;58(5):969-78
references.pmid: 17185738
references.citation: J Mol Biol. 1968 Apr 28;33(2):491-7
references.pmid: 5700707
references.citation: Protein Sci. 1999 Nov;8(11):2366-79
references.pmid: 10595539
references.citation: Nucleic Acids Res. 1994 Nov 11;22(22):4673-80
references.pmid: 7984417
references.citation: Eur J Biochem. 2000 Oct;267(20):6102-9
references.pmid: 11012661