| Characterization of the AGPase large subunit isoforms from tomato indicates that the recombinant L3 subunit is active as a monomer. | |
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MedLine Citation:
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PMID: 20236089 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The enzyme AGPase [ADP-Glc (glucose) pyrophosphorylase] catalyses a rate-limiting step in starch synthesis in tomato (Solanum lycopersicon) fruit, which undergoes a transient period of starch accumulation. It has been a generally accepted paradigm in starch metabolism that the enzyme naturally functions primarily as a heterotetramer comprised of two large subunits (L) and two small subunits (S). The tomato genome harbours a single gene encoding S and three genes for L proteins, which are expressed in both a tissue- and time-specific manner. In the present study the allosteric contributions of the different L subunits were compared by expressing each one in Escherichia coli, in conjunction with S and individually, and characterizing the resulting enzyme activity. Our results indicate different kinetic characteristics of the tomato L1/S and L3/S heterotetramers. Surprisingly, the recombinant L3 protein was also active when expressed alone and size-exclusion and immunoblotting showed that it functioned as a monomer. Subunit interaction modelling pointed to two amino acids potentially affecting subunit interactions. However, directed mutations did not have an impact on subunit tetramerization. These results indicate a hitherto unknown active role for the L subunit in the synthesis of ADP-Glc. |
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Authors:
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Marina Petreikov; Miriam Eisenstein; Yelena Yeselson; Jack Preiss; Arthur A Schaffer |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2010-05-13 |
Journal Detail:
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Title: The Biochemical journal Volume: 428 ISSN: 1470-8728 ISO Abbreviation: Biochem. J. Publication Date: 2010 Jun |
Date Detail:
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Created Date: 2010-05-13 Completed Date: 2010-05-25 Revised Date: 2010-09-22 |
Medline Journal Info:
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Nlm Unique ID: 2984726R Medline TA: Biochem J Country: England |
Other Details:
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Languages: eng Pagination: 201-12 Citation Subset: IM |
Affiliation:
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Department of Vegetable Research, Volcani Center-ARO, Bet Dagan 50250, Israel. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Blotting, Western Escherichia coli / genetics, metabolism Glucose-1-Phosphate Adenylyltransferase / chemistry, genetics, metabolism* Kinetics Lycopersicon esculentum / enzymology*, genetics Mutagenesis, Site-Directed Plant Proteins / chemistry, genetics, metabolism* Protein Isoforms / chemistry, genetics, metabolism* Protein Subunits / chemistry, genetics, metabolism* Recombinant Proteins / chemistry, genetics, metabolism* Tandem Mass Spectrometry |
| Chemical | |
Reg. No./Substance:
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0/Plant Proteins; 0/Protein Isoforms; 0/Protein Subunits; 0/Recombinant Proteins; EC 2.7.7.27/Glucose-1-Phosphate Adenylyltransferase |
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