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Rubisco / CsoS2 N-peptide complex responsible for alpha-carboxysome cargo loading
Structural highlights
FunctionRBL1_HALNC RuBisCO catalyzes two reactions: the carboxylation of D-ribulose 1,5-bisphosphate, the primary event in carbon dioxide fixation, as well as the oxidative fragmentation of the pentose substrate. Both reactions occur simultaneously and in competition at the same active site.[HAMAP-Rule:MF_01338] Publication Abstract from PubMedCarboxysomes 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 alpha-carboxysome, there is little molecular insight into protein-protein interactions that drive the assembly process. Here, studies on the alpha-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 alpha-carboxysome formation. Multivalent interactions between CsoS2 and Rubisco mediate alpha-carboxysome formation.,Oltrogge LM, Chaijarasphong T, Chen AW, Bolin ER, Marqusee S, Savage DF Nat Struct Mol Biol. 2020 Mar;27(3):281-287. doi: 10.1038/s41594-020-0387-7. Epub, 2020 Mar 2. PMID:32123388[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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