THE DISCOVERY OF RUBISCO ACTIVASE - YET ANOTHER STORY OF SERENDIPITY.

Authors: Portis Jr, Archie; Salvucci, Michael

Submitted to: Photosynthesis Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2001
Publication Date: 6/1/2002
Citation: PORTIS JR, A.R., SALVUCCI, M.E. THE DISCOVERY OF RUBISCO ACTIVASE - YET ANOTHER STORY OF SERENDIPITY.. PHOTOSYNTHESIS RESEARCH. 2002. 73:257-264.

Interpretive Summary: In the process of photosynthesis, plants covert light into chemical energy. The energy produced by photosynthesis is then used to synthesize sugars and other foodstuffs. A key enzyme in the process is Rubisco, the enzyme that catalyzes carbon dioxide fixation. The activity of Rubisco is controlled by a second enzyme called Rubisco activase. In this manuscript, we describe the events leading to the discovery and initial chatacterization of Rubisco activase. Highlights include the chance appearance of a peculiar Arabidopsis photosynthesis mutant, missing spots on protein gels, the struggle to develop an enzymatic assay, a fortunate case of contamination, and the controversy over the roles of activase vis-a-vis the Rubisco inhibitor, 2-carboxyarabinitol 1-phosphate, in the light regulation of Rubisco. Review of this discovery provides information on the scientific process that may be useful to younger scientists faced with seemingly intractable research problems.

Technical Abstract: A brief history of Rubisco research and the events leading to the discovery and initial characterization of Rubisco activase are described. Key to the discovery was the chance appearance of a novel Arabidopsis photosynthesis mutant. The characteristics of the mutant suggested that activation of Rubisco was not a spontaneous process in vivo, but involved a heritable factor. A search for the putative factor by 2-D electrophoresis identifie two polypeptides genetically linked to Rubisco activation that were missing in chloroplasts from the mutant. An assay for the activity of these polypeptides which were given the name Rubisco activase was developed after realizing importance of including RuBP in the assay. The requirement for ATP and the subsequent identification of activase as an ATPase came about fortuitously, the result of a RuBP preparation that was contaminated with adenine nucleotides. Finally, the ability of activase to relieve inhibition nof the endogenous Rubisco inhibitor, 2-carboxyarabinitol 1-phosphate, provided an early indication of the mechanism by which activase regulates Rubisco.