Document Type
Article
Publication Date
4-18-2008
Department
Chemistry and Biochemistry
School
Mathematics and Natural Sciences
Abstract
The widely accepted models for the role of carboxysomes in the carbon-concentrating mechanism of autotrophic bacteria predict the carboxysomal carbonic anhydrase to be a crucial component. The enzyme is thought to dehydrate abundant cytosolic bicarbonate and provide ribulose 1.5-bisphosphate carboxylase/oxygenase (RubisCO) sequestered within the carboxysome with sufficiently high concentrations of its substrate, CO2, to permit its efficient fixation onto ribulose 1,5-bisphosphate. In this study, structure and function of carboxysomes purified from wild type Halothiobacillus neapolitanus and from a high CO2-requiring mutant that is devoid of carboxysomal carbonic anhydrase were compared. The kinetic constants for the carbon fixation reaction confirmed the importance of a functional carboxysomal carbonic anhydrase for efficient catalysis by RubisCO. Furthermore, comparisons of the reaction in intact and broken microcompartments and by purified carboxysomal RubisCO implicated the protein shell of the microcompartment as impeding diffusion of CO2 into and out of the carboxysome interior.
Publication Title
Journal of Biological Chemistry
Volume
283
Issue
16
First Page
10377
Last Page
10384
Recommended Citation
Dou, Z.,
Heinhorst, S.,
Williams, E. B.,
Murin, C. D.,
Shively, J. M.,
Cannon, G. C.
(2008). CO2 Fixation Kinetics of Halothiobacillus neapolitanus Mutant Carboxysomes Lacking Carbonic Anhydrase Suggest the Shell Acts as a Diffusional Barrier for CO2. Journal of Biological Chemistry, 283(16), 10377-10384.
Available at: https://aquila.usm.edu/fac_pubs/8955
Comments
http://www.jbc.org/content/283/16/10377.full.pdf+html