Structural and evolutionary relationships among RuBisCOs inferred from their large and small subunits

Area of Science:

• Biochemistry and Molecular Biology
• Structural Biology
• Evolutionary Biology

Background:

• Ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) is crucial for CO2 assimilation in the biosphere.
• Understanding RuBisCO's structural evolution is key to its functional significance and potential improvements.
• RuBisCO comprises large subunit C-terminal (LSC), large subunit N-terminal (LSN), and small subunit (SS) domains.

Purpose of the Study:

• To investigate the functional significance of evolutionary diversification in RuBisCO domains.
• To analyze structural phylogenies of LSC, LSN, and SS domains.
• To explore how structural variations influence RuBisCO's catalytic performance and selectivity.

Main Methods:

• Selection of nonredundant structural data sets for LSC, LSN, and SS domains.
• Utilized QR factorization and QH similarity measure for structural alignment.
• Constructed structural phylogenies to trace evolutionary pathways.

Main Results:

• The LSC domain evolved increased complexity from bacteria/archaea to eukaryotes.
• LSN domain structural variations originated in bacteria and eukaryotes, differing in coil length.
• SS domain variations are linked to the βA-βB-loop region, impacting catalytic performance and CO2/O2 selectivity.

Conclusions:

• Structural variations in RuBisCO domains are linked to evolutionary diversification.
• Observed variations in coil regions significantly influence catalytic efficiency and gas selectivity.
• Findings provide valuable insights for engineering improved RuBisCO enzymes.