2v6a

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Revision as of 08:50, 3 February 2008

CRYSTAL STRUCTURE OF CHLAMYDOMONAS REINHARDTII RUBISCO WITH LARGE-SUBUNIT MUTATIONS V331A, G344S

Overview

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.

About this Structure

2V6A is a Protein complex structure of sequences from Chlamydomonas reinhardtii with , and as ligands. Active as Ribulose-bisphosphate carboxylase, with EC number 4.1.1.39 Known structural/functional Site: . Full crystallographic information is available from OCA.

Reference

Structural Analysis of Altered Large-Subunit Loop-6/Carboxy-Terminus Interactions That Influence Catalytic Efficiency and CO(2)/O(2) 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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