TAILIEUCHUNG - Báo cáo khoa học: Chaperone activity of recombinant maize chloroplast protein synthesis elongation factor, EF-Tu

The protein synthesis elongation factor, EF-Tu, is a protein that carries aminoacyl-tRNA to the A-site of the ribosome during the elongation phase of protein synthesis. In maize (Zea maysL) this protein has been implicated in heat tol-erance, and it hasbeenhypothesizedthatEF-Tuconfersheat tolerance by acting as amolecular chaperone and protecting heat-labile proteins from thermal aggregation and inactiva-tion. In this study we investigated the effect of the recom-binant precursor of maize EF-Tu (pre-EF-Tu) on thermal aggregation and inactivation of the heat-labile proteins, cit-rate synthase and malate dehydrogenase. . | Eur. J. Biochem. 271 3684-3692 2004 FEBS 2004 doi Chaperone activity of recombinant maize chloroplast protein synthesis elongation factor EF-Tu Damodara Rao1 Ivana Momcilovic1 Satoru Kobayashi1 Eduardo Callegari2 and Zoran Ristic1 1 Department of Biology University of South Dakota and department of Basic Biomedical Sciences University of South Dakota School of Medicine Vermillion SD USA The protein synthesis elongation factor EF-Tu is a protein that carries aminoacyl-tRNA to the A-site of the ribosome during the elongation phase of protein synthesis. In maize Zea mays L this protein has been implicated in heat tolerance and it has been hypothesized that EF-Tu confers heat tolerance by acting as a molecular chaperone and protecting heat-labile proteins from thermal aggregation and inactivation. In this study we investigated the effect of the recombinant precursor of maize EF-Tu pre-EF-Tu on thermal aggregation and inactivation of the heat-labile proteins citrate synthase and malate dehydrogenase. The recombinant pre-EF-Tu was purified from Escherichia coli expressing this protein and mass spectrometry confirmed that the isolated protein was indeed maize EF-Tu. The purified protein was capable of binding GDP indicative of protein activity and was stable at 45 C the highest temperature used in this study to test this protein for possible chaperone activity. Importantly the recombinant maize pre-EF-Tu displayed chaperone activity. It protected citrate synthase and malate dehydrogenase from thermal aggregation and inactivation. To our knowledge this is the first observation of chaperone activity by a plant eukaryotic pre-EF-Tu protein. The results of this study support the hypothesis that maize EF-Tu plays a role in heat tolerance by acting as a molecular chaperone and protecting chloroplast proteins from thermal aggregation and inactivation. Keywords chloroplast protein synthesis elongation factor EF-Tu chaperones heat stress heat .

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