Photosynthesis on Earth: evolution of increased complexity and specificity at the dawn of Form I Rubiscos

Structural characterization of AncL+7 and AncL+7 e170N. Alignment of a dimer in AncL+7 co-crystallized without (purple) or with (pink) AncSSU (pink) and CABP, superimposed with an alignment of a dimer in AncL+7 e170N co-crystallized without (teal) or with (orange) AncSSU (beige) and CABP. The respective dimers align to an average effective value of

The evolution of ribulose-1,5-bisphosphate carboxylase/oxygenases (Rubiscos) which strongly discriminate between their substrate carbon dioxide and the undesirable lateral substrate dioxygen has been an important event for photosynthetic organisms adapting to an oxygenated environment.

We use ancestral sequence reconstruction to recapitulate this event. We show that Rubisco increased its specificity and carboxylation efficiency through the gain of an accessory subunit before atmospheric oxygen was present. Using structural and biochemical approaches, we retrace how this subunit was acquired and imposed.

Our work illuminates the emergence of adaptation to increasing ambient oxygen levels, provides a model for studying the function of interactions that have remained elusive due to their essentiality, and sheds light on the determinants of specificity in Rubisco.

Luca Schulz 1, Zhijun Guo 2, Jan Zarzycki 1, Wieland Steinchen 3 4, Jan M Schuller 3 4, Thomas Heimerl 3 5, Simone Prinz 6, Oliver Mueller-Cajar 2, Tobias J Erb 1 3, Georg KA Hochberg 3 4 7

PMID: 36227987 DOI: 10.1126/science.abq1416
pubmed

Evolution of increased complexity and specificity at the dawn of form I Rubiscos, Science

Astrobiology, genomics,

Sharon D. Cole