Source:http://linkedlifedata.com/resource/pubmed/id/17824672
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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
39
|
| pubmed:dateCreated |
2007-9-25
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| pubmed:databankReference | |
| pubmed:abstractText |
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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| pubmed:language |
eng
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| pubmed:journal | |
| pubmed:citationSubset |
IM
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| pubmed:chemical | |
| pubmed:status |
MEDLINE
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| pubmed:month |
Oct
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| pubmed:issn |
0006-2960
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| pubmed:author | |
| pubmed:issnType |
Print
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| pubmed:day |
2
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| pubmed:volume |
46
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| pubmed:owner |
NLM
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| pubmed:authorsComplete |
Y
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| pubmed:pagination |
11080-9
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| pubmed:meshHeading |
pubmed-meshheading:17824672-Algal Proteins,
pubmed-meshheading:17824672-Amino Acid Substitution,
pubmed-meshheading:17824672-Animals,
pubmed-meshheading:17824672-Binding Sites,
pubmed-meshheading:17824672-Carbon Dioxide,
pubmed-meshheading:17824672-Catalysis,
pubmed-meshheading:17824672-Chlamydomonas reinhardtii,
pubmed-meshheading:17824672-Chloroplasts,
pubmed-meshheading:17824672-Crystallography, X-Ray,
pubmed-meshheading:17824672-Models, Molecular,
pubmed-meshheading:17824672-Mutagenesis, Site-Directed,
pubmed-meshheading:17824672-Mutation,
pubmed-meshheading:17824672-Oxygen,
pubmed-meshheading:17824672-Protein Binding,
pubmed-meshheading:17824672-Protein Structure, Secondary,
pubmed-meshheading:17824672-Protein Structure, Tertiary,
pubmed-meshheading:17824672-Ribulose-Bisphosphate Carboxylase,
pubmed-meshheading:17824672-Substrate Specificity
|
| pubmed:year |
2007
|
| pubmed:articleTitle |
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.
|
| pubmed:affiliation |
Department of Molecular Biology, Swedish University of Agricultural Sciences, BMC Box 590, 751 24 Uppsala, Sweden.
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| pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, Non-P.H.S.,
Research Support, Non-U.S. Gov't
|