Novel Bacterial Clade Reveals Origin of Form I Rubisco

Rubisco sustains the biosphere through the fixation of CO2 into biomass.

The Science

All plant biomass is sourced from the carbon-fixing enzyme Rubisco.

Although there is significant interest in engineering Rubisco to improve overall plant productivity, there has been little progress in the field.

All plants contain Form I Rubisco, and all Form I Rubisco consist of both eight Large (RbcL) and eight Small (RbcS) subunits. No Form I Rubisco has previously been discovered to lack the small subunit, which would represent a key transition in Rubisco evolution.

Researchers synthesized, expressed, purified, and biochemically characterized the novel enzyme. Solved solution state and crystal structure of novel Form I’ Rubisco.

Understanding how Rubisco evolved may provide unique insight into engineering Rubisco.

The Impact

Through metagenomic analyses, researchers discovered a previously uncharacterized clade sister to form I Rubisco that evolved without small subunits. This clade diverged before the evolution of cyanobacteria and the origin of the small subunit; thus, it provides a unique reference point to advance understanding of form I Rubisco evolution. Structural and kinetic data presented here reveal how a proto-form I Rubisco assembled and functioned without the structural stability imparted from small subunits.


Banda, D. M., J. H. Pereira, A. K. Liu, D. J. Orr, M. Hammel, C. He, M. A. J. Parry, E. Carmo-Silva, P. D. Adams, J. F. Banfield, and P. M. Shih. 2020. “Novel Bacterial Clade Reveals Origin of Form I Rubisco,Nature Plants 6, 1158–66. DOI:10.1038/s41477-020-00762-4.