Multivalent interactions between CsoS2 and Rubisco mediate ?-carboxysome formation.

ABSTRACT: 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 ?-carboxysome, there is little molecular insight into protein-protein interactions that drive the assembly process. Here, studies on the ?-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 ?-carboxysome formation.

SUBMITTER: Oltrogge LM 

PROVIDER: S-EPMC7337323 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature