infocus #69 March 2023 Investigating the liquid phase separation of Rubisco and Linker proteins in vitro

Most of the oxygen we breathe finds its origins in marine algal photosynthesis. These algae organise their Rubisco, the enzyme responsible for capturing carbon dioxide and releasing oxygen, into a liquid droplet called the ‘pyrenoid’.

10.22443/rms.inf.1.247

The algae then concentrate carbon dioxide into the liquid, and the reactions can run faster. The pyrenoid improves the efficiency of the oxygen-producing reaction by around 60% compared to the same reaction in plant leaves.

Understanding the phase-separation process will help scientists introduce these carbon concentration mechanisms into plants, with the hope of increasing crop yields to help with food security. However, for these liquid droplets to form at all, Rubisco requires a counterpart ‘linker’ protein. We don’t know what minimal properties of a linker protein are needed for pyrenoids to function this way. And why a liquid? What are the resulting properties of the droplet that drive this incredible boost in photosynthetic output?