Download MendeleyAssembly mechanism of the beta-carboxysome shell mediated by the chaperone CcmS.
Li, J., Deng, J.X., Chen, X., Li, B., Li, B.R., Zhu, Z.L., Liu, J., Chen, Y., Mi, H., Zhou, C.Z., Jiang, Y.L.(2025) New Phytol 246: 1676-1690
- PubMed: 40125605
- DOI: https://doi.org/10.1111/nph.70086
- Primary Citation of Related Structures:
9IUR, 9IV3, 9IV7 - PubMed Abstract:
Carboxysomes are self-assembled bacterial microcompartments (BMCs) that encapsulate the enzymes RuBisCO and carbonic anhydrase into a proteinaceous shell, enhancing the efficiency of photosynthetic carbon fixation. The chaperone CcmS was reported to participate in the assembly of β-carboxysomes; however, the underlying molecular mechanism remains elusive. We report the crystal structure of CcmS from Synechocystis sp. PCC 6803, revealing a monomer of α/β fold. Moreover, its complex structures with two types of BMC hexamers, CcmK1 homohexamer and CcmK1-CcmK2 heterohexamer, reveal a same pattern of CcmS binding to the featured C-terminal segment of CcmK1. Upon binding to CcmS, this C-terminal segment of CcmK1 is folded into an amphipathic α-helix protruding outward that might function as a hinge to crosslink adjacent BMC-H hexamers, thereby facilitating concerted and precise assembly of the β-carboxysome shell. Deletion of the ccmS gene or the 8-residue C-terminal coding region of ccmK1 resulted in the formation of aberrant and fewer carboxysomes, suppressed photosynthetic capacity in Synechocystis sp. PCC 6803. These findings enable us to propose a putative model for the chaperone-assisted assembly of β-carboxysome shell and provide clues for the design and engineering of efficient carbon fixation machinery.
- School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230027, China.
Organizational Affiliation:
