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 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.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Amino Acid Sequence
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Bacterial Proteins / chemistry*
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism
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Binding Sites
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Carbon Cycle / physiology
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Cloning, Molecular
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Crystallography, X-Ray
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Escherichia coli / genetics
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Escherichia coli / metabolism
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Gene Expression
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Genetic Vectors / chemistry
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Genetic Vectors / metabolism
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Halothiobacillus / chemistry*
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Halothiobacillus / genetics
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Halothiobacillus / metabolism
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Intrinsically Disordered Proteins / chemistry*
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Intrinsically Disordered Proteins / genetics
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Intrinsically Disordered Proteins / metabolism
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Models, Molecular
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Organelles / chemistry*
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Organelles / metabolism
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Protein Binding
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Protein Conformation, alpha-Helical
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Protein Conformation, beta-Strand
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Protein Interaction Domains and Motifs
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Protein Multimerization
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Recombinant Proteins / chemistry
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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Ribulose-Bisphosphate Carboxylase / chemistry*
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Ribulose-Bisphosphate Carboxylase / genetics
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Ribulose-Bisphosphate Carboxylase / metabolism
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Sequence Alignment
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Sequence Homology, Amino Acid
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Static Electricity
Substances
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Bacterial Proteins
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Intrinsically Disordered Proteins
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Recombinant Proteins
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Ribulose-Bisphosphate Carboxylase