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bioRxiv · 10.1101/708164

α-carboxysome formation is mediated by the multivalent and disordered protein CsoS2

Oltrogge, L. M.·Chaijarasphong, T.·Chen, A. W.·Bolin, E. R.·Marqusee, S.·Savage, D. F.
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Abstract

Carboxysomes are bacterial microcompartments that function as the centerpiece of the bacterial CO2-concentrating mechanism, feeding high concentrations of CO2 to the enzyme Rubisco for fixation. The carboxysome self-assembles from thousands of individual proteins into icosahedral-like particles with a dense enzyme cargo encapsulated within a proteinaceous shell. In the case of the -carboxysome, there is little molecular insight into protein-protein interactions which drive the assembly process. Here we show that the N-terminus of CsoS2, an intrinsically disordered protein found in the -carboxysome, possesses a repeated peptide sequence that binds Rubisco. X-ray structural analysis of the peptide bound to Rubisco reveals a series of conserved electrostatic interactions that are only made with properly assembled hexadecameric Rubisco. Although biophysical measurements indicate this single interaction is weak, its implicit multivalency induces high-affinity binding through avidity. Taken together, our results indicate CsoS2 acts as an interaction hub to condense Rubisco and enable efficient -carboxysome formation.

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Oltrogge, L. M., Chaijarasphong, T., Chen, A. W., Bolin, E. R., Marqusee, S., Savage, D. F.. 2019-07-19. α-carboxysome formation is mediated by the multivalent and disordered protein CsoS2. https://doi.org/10.1101/708164

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