Browsing by Author "California Institute for Quantitative Biosciences"

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    Multivalent interactions between CsoS2 and Rubisco mediate α-carboxysome formation
    (2020-03-01) Luke M. Oltrogge; Thawatchai Chaijarasphong; Allen W. Chen; Eric R. Bolin; Susan Marqusee; David F. Savage; California Institute for Quantitative Biosciences; University of California, Berkeley; Mahidol University
    © 2020, The Author(s), under exclusive licence to Springer Nature America, Inc. Carboxysomes are bacterial microcompartments that function as the centerpiece of the bacterial CO2-concentrating mechanism by facilitating high CO2 concentrations near the carboxylase Rubisco. 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 α-carboxysome, there is little molecular insight into protein–protein interactions that drive the assembly process. Here, studies on the α-carboxysome from Halothiobacillus neapolitanus demonstrate that Rubisco interacts with the N terminus of CsoS2, a multivalent, intrinsically disordered protein. X-ray structural analysis of the CsoS2 interaction motif bound to Rubisco reveals a series of conserved electrostatic interactions that are only made with properly assembled hexadecameric Rubisco. Although biophysical measurements indicate that this single interaction is weak, its implicit multivalency induces high-affinity binding through avidity. Taken together, our results indicate that CsoS2 acts as an interaction hub to condense Rubisco and enable efficient α-carboxysome formation.