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Title: ACTIVATION OF RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE/OXYGENASE (RUBISCO) WITH CHIMERIC ACTIVASE PROTEINS

Author
item ESAU, BRIAN - PLANT BIOLOGY UOFI URBANA
item SYNDER, GORDON - USDA/ARS/PRU URBANA IL
item PORTIS JR, ARCHIE

Submitted to: Photosynthesis Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/1998
Publication Date: N/A
Citation: Esau, B.D., Synder, G.W., Portis Jr, A.R. 1998. Activation of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) with chimeric activase proteins. Photosynthesis Research. 58:175-181.

Interpretive Summary: The activity of Rubisco, the enzyme that captures carbon dioxide, often limits photosynthesis, the process by which plants use light energy from the sun to make carbohydrates for growth from carbon dioxide and water. The activity of Rubisco is determined and hence regulated by another enzyme known as Rubisco activase. Rubisco activity might be increased to improve plant growth by altering its regulation, but critical details of the regulatory mechanism need to be ascertained. In this study, we identified a domain in the amino acid sequence of Rubisco activase that is interacting with Rubisco during the regulation process. This information will benefit scientists attempting to modify the properties and regulation of Rubisco in ways beneficial for increased photosynthesis by crop plants.

Technical Abstract: The Rubisco activase amino acid sequences of spinach and tobacco are 79 percent identical, yet the tobacco protein does not facilitate the activation of the uncarbamylated, ribulose bisphosphate bound form of spinach ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) and vice versa. In contrast, combinations of the spinach Rubisco activase with Rubisco from other species are almost as effective as the homologous combination. To examine the basis of the preference of activase for the analogous Rubisco, several recombinant chimeric proteins were obtained by combining regions from the DNA's of spinach and tobacco activase and expression in Escherichia coli. The chimeric proteins were analyzed for ATP hydrolysis and ability to activate spinach and tobacco Rubisco. Comparisons of Rubisco preference with composition of the various activase chimeras indicate that the major determinants of Rubisco preference seem to be localized in the carboxyl-terminal region.