Poster Presentation The 47th Lorne Conference on Protein Structure and Function 2022

Encapsulins as synthetic organelles for improved carbon fixation (#245)

Taylor N Szyszka 1 , Timothy M Rhodes 2 , Spencer Whitney 2 , Yu Heng Lau 1
  1. School of Chemistry , The University of Sydney, Sydney , NSW, Australia
  2. Plant Sciences Division, Research School of Biology , The Australian National University , Canberra, ACT, Australia

Ribulose 1,5- Bisphosphate Carboxylase Oxygenase (RuBisCO) is one of the most important enzymes on the planet. Responsible for the carbon fixation step of photosynthesis, it underpins all of life. Despite its crucial role, RuBisCO is still an incredibly inefficient and poorly selective enzyme, often confusing its CO2 substrate with O2, leading to the energy-intensive and wasteful photorespiration pathway.  To compensate for this, many photosynthetic organisms have developed Carbon-Concentrating Mechanisms (CCM’s) to enhance RuBisCO performance. One such CCM includes carboxysomes,1 which are protein-bound compartments housing RuBisCO and the CO2-producing enzyme carbonic anhydrase within a protein shell suggested to have a selectively permeable character2. Carboxysomes are quite effective, and many researchers have sought to transplant these organelles into orthogonal organisms. While success has been found in certain cases1,3, it is not trivial to produce and assemble proper carboxysomes in non-native organisms due to the large number of required genes and the inherent complexity of the system. To alleviate these complexities, our lab is seeking to recapitulate a carboxysome-like system within a much simpler encapsulin protein cage. Encapsulins are nanoscale protein cages which self-assemble from many copies of a single monomer unit4. We endeavour to encapsulate RuBisCO and carbonic anhydrase within the encapsulin shell to enhance RuBisCO efficiency, with the grander goal of inserting this system into plants or other photosynthetic organisms to enhance carbon fixation and photosynthesis. The poster will present our work to date on this project.

  1. Borden, J. S. & Savage, D. F. New discoveries expand possibilities for carboxysome engineering. Curr. Opin. Microbiol. 61, 58–66 (2021).
  2. Faulkner, M. et al. Molecular simulations unravel the molecular principles that mediate selective permeability of carboxysome shell protein. Sci. Rep. 10, 1–14 (2020).
  3. Long, B. M. et al. Carboxysome encapsulation of the CO 2-fixing enzyme Rubisco in tobacco chloroplasts. Nat. Commun. 9, 1–14 (2018).
  4. Nichols, R. J., Cassidy-Amstutz, C., Chaijarasphong, T. & Savage, D. F. Encapsulins: molecular biology of the shell. Crit. Rev. Biochem. Mol. Biol. 52, 583–594 (2017).