Likely the most abundant enzyme on Earth, Rubisco performs the vital function of fixing carbon from the environment in photosynthetic organisms. Of the four forms of Rubisco known to exist today, form I—present in cyanobacteria, some algae, and plants—has the highest specificity for carbon dioxide and the most efficient catalytic activity. Researchers reconstructed ancestral Rubisco sequences and measured how well these revived putative proteins performed in a lab setting, proposing in a study published online yesterday (October 13) in Science that form I’s improved qualities were acquired thanks to the gain of a small subunit. In the study, the authors retrace how this transition could have taken place.
Form I Rubisco is made up of eight identical catalytic large subunits and eight identical small subunits. Researchers long suspected that its enhanced ability to discriminate CO2 from the chemically similar molecule oxygen (O2) could be related to the presence of these ...
