Visualizing Individual RuBisCO and Its Assembly into Carboxysomes in Marine Cyanobacteria by Cryo-Electron Tomography

Wei Dai, Muyuan Chen, Christopher Myers, Steven J. Ludtke, B. Montgomery Pettitt, Jonathan A. King, Michael F. Schmid, Wah Chiu

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Cyanobacteria are photosynthetic organisms responsible for ~ 25% of the organic carbon fixation on earth. A key step in carbon fixation is catalyzed by ribulose bisphosphate carboxylase/oxygenase (RuBisCO), the most abundant enzyme in the biosphere. Applying Zernike phase-contrast electron cryo-tomography and automated annotation, we identified individual RuBisCO molecules and their assembly intermediates leading to the formation of carboxysomes inside Syn5 cyanophage infected cyanobacteria Synechococcus sp. WH8109 cells. Surprisingly, more RuBisCO molecules were found to be present as cytosolic free-standing complexes or clusters than as packaged assemblies inside carboxysomes. Cytosolic RuBisCO clusters and partially assembled carboxysomes identified in the cell tomograms support a concurrent assembly model involving both the protein shell and the enclosed RuBisCO. In mature carboxysomes, RuBisCO is neither randomly nor strictly icosahedrally packed within protein shells of variable sizes. A time-averaged molecular dynamics simulation showed a semi-liquid probability distribution of the RuBisCO in carboxysomes and correlated well with carboxysome subtomogram averages. Our structural observations reveal the various stages of RuBisCO assemblies, which could be important for understanding cellular function.

Original languageEnglish (US)
Pages (from-to)4156-4167
Number of pages12
JournalJournal of Molecular Biology
Issue number21
StatePublished - Oct 19 2018


  • RuBisCO
  • carboxysome biogenesis
  • convolutional neural network-based annotation
  • molecular dynamics simulation
  • zernike phase-contrast cryo-electron tomography

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Molecular Biology


Dive into the research topics of 'Visualizing Individual RuBisCO and Its Assembly into Carboxysomes in Marine Cyanobacteria by Cryo-Electron Tomography'. Together they form a unique fingerprint.

Cite this