title: Chloroplast protein synthesis elongation factor, EF-Tu, reduces thermal aggregation of rubisco activase.
abstract: Chloroplast protein synthesis elongation factor, EF-Tu, has been implicated in heat tolerance in maize. The recombinant precursor of this protein, pre-EF-Tu, has been found to exhibit chaperone activity and protect heat-labile proteins, such as citrate synthase and malate dehydrogenase, from thermal aggregation. Chloroplast EF-Tu is highly conserved and it is possible that the chaperone activity of this protein is not species-specific. In this study, we investigated the effect of native wheat pre-EF-Tu on thermal aggregation of rubisco activase. Additionally, we investigated the effect of native and recombinant maize pre-EF-Tu on activase aggregation. Activase was chosen because it displays an exceptional sensitivity to thermal aggregation and constrains photosynthesis at high temperature. The native precursors of both wheat and maize EF-Tu displayed chaperone activity, as shown by the capacity of both proteins to reduce thermal aggregation of rubisco activase in vitro. Similarly, the recombinant maize pre-EF-Tu protected activase from thermal aggregation. This is the first report on chaperone activity of native pre-EF-Tu and the first evidence for thermal protection of a photosynthetic enzyme by this putative chaperone. The results are consistent with the hypothesis that chloroplast EF-Tu plays a functional role in heat tolerance by acting as a molecular chaperone.
authors.affiliation: United States Department of Agriculture - Agricultural Research Service, Plant Science and Entomology Research Unit, 4008 Throckmorton Hall, Manhattan, KS 66506, USA. zoran.ristic@gmprc.ksu.edu
authors.forename: Zoran
authors.initials: Z
authors.lastname: Ristic
authors.forename: Ivana
authors.initials: I
authors.lastname: Momcilović
authors.forename: Jianming
authors.initials: J
authors.lastname: Fu
authors.forename: Eduardo
authors.initials: E
authors.lastname: Callegari
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: DeRidder
mesh_terms: D002736:Chloroplasts / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D015151:Immunoblotting; D010444:Peptide Elongation Factor Tu / Q000302:isolation & purification / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification; D014176:Protein Biosynthesis; D011498:Protein Precursors / Q000378:metabolism; D020836:Protein Structure, Quaternary; D011994:Recombinant Proteins / Q000378:metabolism; D012995:Solubility; D013696:Temperature; D014908:Triticum / Q000378:metabolism*; D003313:Zea mays / Q000201:enzymology*
chemical_list: D010940:Plant Proteins; D011498:Protein Precursors; D011994:Recombinant Proteins; C054765:rca protein, plant; D010444:Peptide Elongation Factor Tu