Part:BBa_K5115026

csoS2

Introduction

CsoS2 is an essential protein involved in the assembly and formation of α-carboxysomes, which are bacterial microcompartments designed to encapsulate enzymes such as ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) for carbon fixation. The carboxysome shell, composed of various proteins, serves as a selectively permeable barrier, facilitating the flux of specific metabolites while protecting enzymes from external inhibitors like oxygen. CsoS2 plays a crucial role in mediating the self-assembly of the shell and is functionally analogous to linking proteins found in β-carboxysomes, like CcmM. In the chemoautotrophic bacterium Halothiobacillus neapolitanus, CsoS2 is present in two isoforms (CsoS2A and CsoS2B), which together drive the formation of ordered, virus-like protein shells in E. coli.

Usage and Biology

In the assembly of α-carboxysomes, CsoS2 is vital not only for shell formation but also for cargo encapsulation. This protein interacts with other shell components to organize the structure and recruit internal enzymes. The N-terminal region of CsoS2 facilitates interactions with Rubisco, ensuring its appropriate encapsulation within the carboxysome. CsoS2's C-terminal region acts as an encapsulation peptide (EP), linking the shell to external enzymes and directing their incorporation into the microcompartment. This mechanism was demonstrated by fusing CsoS2 with enhanced green fluorescent protein (GFP) in E. coli, which resulted in the formation of highly organized shell structures capable of encapsulating GFP-tagged proteins.

The functional importance of CsoS2 has also been highlighted in studies on hydrogenase encapsulation. By leveraging the shell's ability to create an oxygen-limited environment, CsoS2-mediated shells were used to encapsulate oxygen-sensitive [FeFe]-hydrogenases, demonstrating enhanced catalytic performance for hydrogen production. This encapsulation improved the enzymes' oxygen tolerance and preserved their catalytic activity, making CsoS2 a valuable tool in the construction of synthetic nanoreactors for biohydrogen production and other biotechnological applications.

Characterization

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  INCOMPATIBLE WITH RFC[12]

  Illegal NheI site found at 133
  
• 21
  INCOMPATIBLE WITH RFC[21]

  Illegal BglII site found at 291
  
• 23
  COMPATIBLE WITH RFC[23]
• 25
  INCOMPATIBLE WITH RFC[25]

  Illegal AgeI site found at 799
  Illegal AgeI site found at 1750
  Illegal AgeI site found at 2431
  
• 1000
  INCOMPATIBLE WITH RFC[1000]

  Illegal SapI site found at 191
  

References

[1] Li, T., Jiang, Q., Huang, J., Aitchison, C. M., Huang, F., Yang, M., Dykes, G. F., He, H. L., Wang, Q., Sprick, R. S., Cooper, A. I., & Liu, L. N. (2020). Reprogramming bacterial protein organelles as a nanoreactor for hydrogen production. Nature communications, 11(1), 5448. https://doi.org/10.1038/s41467-020-19280-0

[2] Oltrogge, L. M., Chaijarasphong, T., Chen, A. W., Bolin, E. R., Marqusee, S., & Savage, D. F. (2020). Multivalent interactions between CsoS2 and Rubisco mediate α-carboxysome formation. Nature structural & molecular biology, 27(3), 281–287. https://doi.org/10.1038/s41594-020-0387-7