Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign Rubisco is arguably the most abundant–and most important–protein on Earth. This enzyme drives photosynthesis, the process that plants use to convert sunlight into energy to fuel crop growth and yield. Rubisco’s role is to capture and fix carbon dioxide (CO 2) into sugar that fuels the plant’s activities. However, as much as Rubisco benefits plant growth, it also can operate at a notoriously slow pace that creates a hindrance to photosynthetic efficiency. About 20 percent of the time Rubisco fixes oxygen (O 2) molecules instead of CO