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2v68

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{{STRUCTURE_2v68| PDB=2v68 | SCENE= }}
{{STRUCTURE_2v68| PDB=2v68 | SCENE= }}
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'''CRYSTAL STRUCTURE OF CHLAMYDOMONAS REINHARDTII RUBISCO WITH LARGE-SUBUNIT MUTATIONS V331A, T342I'''
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===CRYSTAL STRUCTURE OF CHLAMYDOMONAS REINHARDTII RUBISCO WITH LARGE-SUBUNIT MUTATIONS V331A, T342I===
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==Overview==
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The loop between alpha-helix 6 and beta-strand 6 in the alpha/beta-barrel of ribulose-1,5-bisphosphate carboxylase/oxygenase plays a key role in discriminating between CO2 and O2. Genetic screening in Chlamydomonas reinhardtii previously identified a loop-6 V331A substitution that decreases carboxylation and CO2/O2 specificity. Revertant selection identified T342I and G344S substitutions that restore photosynthetic growth by increasing carboxylation and specificity of the V331A enzyme. In numerous X-ray crystal structures, loop 6 is closed or open depending on the activation state of the enzyme and the presence or absence of ligands. The carboxy terminus folds over loop 6 in the closed state. To study the molecular basis for catalysis, directed mutagenesis and chloroplast transformation were used to create T342I and G344S substitutions alone. X-ray crystal structures were then solved for the V331A, V331A/T342I, T342I, and V331A/G344S enzymes, as well as for a D473E enzyme created to assess the role of the carboxy terminus in loop-6 closure. V331A disturbs a hydrophobic pocket, abolishing several van der Waals interactions. These changes are complemented by T342I and G344S, both of which alone cause decreases in CO2/O2 specificity. In the V331A/T342I revertant enzyme, Arg339 main-chain atoms are displaced. In V331A/G344S, alpha-helix 6 is shifted. D473E causes disorder of the carboxy terminus, but loop 6 remains closed. Interactions between a transition-state analogue and several residues are altered in the mutant enzymes. However, active-site Lys334 at the apex of loop 6 has a normal conformation. A variety of subtle interactions must be responsible for catalytic efficiency and CO2/O2 specificity.
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{{ABSTRACT_PUBMED_17824672}}
==About this Structure==
==About this Structure==
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[[Category: Rubisco]]
[[Category: Rubisco]]
[[Category: Transit peptide]]
[[Category: Transit peptide]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 13:43:24 2008''

Revision as of 10:43, 28 July 2008

Image:2v68.png

Template:STRUCTURE 2v68

CRYSTAL STRUCTURE OF CHLAMYDOMONAS REINHARDTII RUBISCO WITH LARGE-SUBUNIT MUTATIONS V331A, T342I

Template:ABSTRACT PUBMED 17824672

About this Structure

2V68 is a Protein complex structure of sequences from Chlamydomonas reinhardtii. Full crystallographic information is available from OCA.

Reference

Structural analysis of altered large-subunit loop-6/carboxy-terminus interactions that influence catalytic efficiency and CO2/O2 specificity of ribulose-1,5-bisphosphate carboxylase/oxygenase., Karkehabadi S, Satagopan S, Taylor TC, Spreitzer RJ, Andersson I, Biochemistry. 2007 Oct 2;46(39):11080-9. Epub 2007 Sep 8. PMID:17824672

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