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| | {{STRUCTURE_1ddi| PDB=1ddi | SCENE= }} | | {{STRUCTURE_1ddi| PDB=1ddi | SCENE= }} |
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| - | '''CRYSTAL STRUCTURE OF SIR-FP60'''
| + | ===CRYSTAL STRUCTURE OF SIR-FP60=== |
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| - | ==Overview==
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| - | Escherichia coli NADPH-sulfite reductase (SiR) is a 780 kDa multimeric hemoflavoprotein composed of eight alpha-subunits (SiR-FP) and four beta-subunits (SiR-HP) that catalyses the six electron reduction of sulfite to sulfide. Each beta-subunit contains a Fe4S4 cluster and a siroheme, and each alpha-subunit binds one FAD and one FMN as prosthetic groups. The FAD gets electrons from NADPH, and the FMN transfers the electrons to the metal centers of the beta-subunit for sulfite reduction. We report here the 1.94 A X-ray structure of SiR-FP60, a recombinant monomeric fragment of SiR-FP that binds both FAD and FMN and retains the catalytic properties of the native protein. The structure can be divided into three domains. The carboxy-terminal part of the enzyme is composed of an antiparallel beta-barrel which binds the FAD, and a variant of the classical pyridine dinucleotide binding fold which binds NADPH. These two domains form the canonic FNR-like module, typical of the ferredoxin NADP+ reductase family. By analogy with the structure of the cytochrome P450 reductase, the third domain, composed of seven alpha-helices, is supposed to connect the FNR-like module to the N-terminal flavodoxine-like module. In four different crystal forms, the FMN-binding module is absent from electron density maps, although mass spectroscopy, amino acid sequencing and activity experiments carried out on dissolved crystals indicate that a functional module is present in the protein. Our results clearly indicate that the interaction between the FNR-like and the FMN-like modules displays lower affinity than in the case of cytochrome P450 reductase. The flexibility of the FMN-binding domain may be related, as observed in the case of cytochrome bc1, to a domain reorganisation in the course of electron transfer. Thus, a movement of the FMN-binding domain relative to the rest of the enzyme may be a requirement for its optimal positioning relative to both the FNR-like module and the beta-subunit.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_10860732}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 10860732 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_10860732}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Fnr]] | | [[Category: Fnr]] |
| | [[Category: Modular protein]] | | [[Category: Modular protein]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 13:43:35 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 22:51:41 2008'' |
Revision as of 19:51, 30 June 2008
Template:STRUCTURE 1ddi
CRYSTAL STRUCTURE OF SIR-FP60
Template:ABSTRACT PUBMED 10860732
About this Structure
1DDI is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
Reference
Four crystal structures of the 60 kDa flavoprotein monomer of the sulfite reductase indicate a disordered flavodoxin-like module., Gruez A, Pignol D, Zeghouf M, Coves J, Fontecave M, Ferrer JL, Fontecilla-Camps JC, J Mol Biol. 2000 May 26;299(1):199-212. PMID:10860732
Page seeded by OCA on Mon Jun 30 22:51:41 2008
