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United States Department of Agriculture

Agricultural Research Service

Title: Chloroplast EF-Tu and thermal aggregation of Rubisco activase

Authors
item Ristic, Zoran
item Momcilovic, Ivana - KANSAS STATE UNIVERSITY
item Fu, Jianming - KANSAS STATE UNIVERSITY
item Callegari, Eduardo - UNIVERSITY OF SOUTH DAKOT
item Deridder, Benjamin

Submitted to: Journal of Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 13, 2007
Publication Date: July 13, 2007
Citation: Ristic, Z., Momcilovic, I., Fu, J., Callegari, E., Deridder, B.P. 2007. Chloroplast EF-Tu and thermal aggregation of Rubisco activase. Journal of Physiology.164:1564-1571.

Interpretive Summary: A plant protein, known as chloroplast EF-Tu, has been implicated in heat tolerance in maize. This protein has been found to protect heat-labile proteins, such as citrate synthase and malate dehydrogenase, from heat-induced damage (thermal aggregation). In this study, we investigated the effect of wheat EF-Tu on thermal aggregation of a photosynthetic enzyme, Rubisco activase. Additionally, we investigated the effect of maize EF-Tu on activase aggregation. Activase was chosen because it displays an exceptional sensitivity to thermal aggregation and constrains photosynthesis at high temperature. Both wheat and maize EF-Tu protected Rubisco activase from thermal aggregation. This is the first report on protective activity of wheat EF-Tu and the first evidence for thermal protection of a photosynthetic enzyme by this chloroplast protein. The results are consistent with the hypothesis that chloroplast EF-Tu plays a functional role in heat tolerance by protecting heat-labile proteins from heat-induced damage.

Technical 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.

Last Modified: 9/20/2014
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