It has been a longstanding goal to enhance the performance of the CO2 fixing enzyme Rubisco in crop plants. The highly divergent red-type Form ID Rubiscos found in the red plastid lineage frequently possess interesting kinetic properties, such as high CO2/O2 specificities. In addition they are very often found sequestered in biomolecular condensates known as pyrenoids. Pyrenoids permit localized elevation of the concentration of Rubisco's substrate CO2, which minimizes the wasteful oxygenation reaction. Unfortunately eukaryotic red Rubiscos cannot currently be functionally produced in other organisms and knowledge about their pyrenoids is still sparse.
I will discuss my groups' efforts to understand the molecular framework underpinning "red" pyrenoids and our progress towards making red eukaryotic Rubiscos amenable to utilization in heterologous systems such as plants. The characterization of the multivalent Rubisco linker protein PYCO1 in the diatom Phaeodactylum tricornutum led to the identification of sticker motifs involved in binding the carboxylase. Examination of proteomic and genomic data led to the identification of multiple additional multivalent Rubisco binding proteins, which also localize to the pyrenoid. We are using a combination of genetic and mechanistic biochemical approaches to dissect the birth, life and death of the red Rubiscos. This knowledge is generated in the hope that it will contribute to future reductions in photorespiratory energy losses.