The scientists structurally characterized the newly discovered tetrameric rubisco with the aid of crystallography and small-angle x-ray scattering (SAXS). Then they retraced the evolution of ancestral and extant form II rubisco, which revealed a complex and diverse history of oligomerization (Science Advances, August 26, 2022).

The reconstruction suggests the form II rubisco gene has changed over its evolutionary history to produce proteins with a range of structures that transform into new shapes or revert back to older structures with ease. Before this research, it was assumed most protein assemblies were entrenched over time by selective pressure to refine their function, but this research contradicts that notion. In other words, the research team has learned proteins display structural plasticity, much more so than they believed.

They also conducted mutational experiments to see how altering the rubisco assembly affected the enzyme's activity. This induced mutation produced a form of rubisco that is better at using its target molecule, CO2. All naturally occurring rubisco frequently binds the similarly sized O2 molecule by accident, lowering the enzyme's productivity.

Because there are mutations outside of the active site that participate in this activity and can potentially change protein function, that opens the doors to future avenues of research, the scientists said.