structural analysis of csos1a and the protein shell of the halothiobacillus neapolitanus carboxysomecsos1a结构分析和蛋白质外壳的halothiobacillus neapolitanus carboxysome.pdf

PLoS BIOLOGY Structural Analysis of CsoS1A and the Protein Shell of the Halothiobacillus neapolitanus Carboxysome 1 1,2,3 4 4 4 4 Yingssu Tsai , Michael R. Sawaya , Gordon C. Cannon , Fei Cai , Eric B. Williams , Sabine Heinhorst , Cheryl A. Kerfeld1,3,5, Todd O. Yeates1,2,3* 1 Molecular Biology Institute, University of California Los Angeles, Los Angeles, California, United States of America, 2 Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, United States of America, 3 University of California Los Angeles–United States Department of Energy Institute for Genomics and Proteomics, Los Angeles, California, United States of America, 4 Department of Chemistry and Biochemistry, University of Southern Mississippi, Hattiesburg, Mississippi, United States of America, 5 Life Sciences Core, University of California Los Angeles, Los Angeles, California, United States of America The carboxysome is a bacterial organelle that functions to enhance the efficiency of CO2 fixation by encapsulating the enzymes ribulose bisphosphate carboxylase/oxygenase (RuBisCO) and carbonic anhydrase. The outer shell of the carboxysome is reminiscent of a viral capsid, being constructed from many copies of a few small proteins. Here we describe the structure of the shell protein CsoS1A from the chemoautotrophic bacterium Halothiobacillus neapolitanus. The CsoS1A protein forms hexameric units that pack tightly together to form a molecular layer, which is perforated by narrow pores. Sulfate ions, soaked into crystals of CsoS1A, are observed in the pores of the molecular layer, supporting the idea that the pores could be the conduit for negatively charged m