Selective Permeability of Carboxysome Shell Pores to Anionic Molecules

Mahinthichaichan, P.; Morris, D. M.; Wang, Y.; Jensen, G. J.; Tajkhorshid, E.

doi:10.1101/367714

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bioRxiv · 10.1101/367714

Selective Permeability of Carboxysome Shell Pores to Anionic Molecules

Mahinthichaichan, P.·Morris, D. M.·Wang, Y.·Jensen, G. J.·Tajkhorshid, E.

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Abstract

Carboxysomes are closed polyhedral cellular microcompartments that increase the efficiency of carbon fixation in autotrophic bacteria. Carboxysome shells consist of small proteins that form hexameric units with semi-permeable central pores containing binding sites for anions. This feature is thought to selectively allow access to RuBisCO enzymes inside the carboxysome by [Formula] (the dominant form of CO2 in the aqueous solution at pH 7.4) but not O2, which leads to a non-productive reaction. To test this hypothesis, here we use molecular dynamics simulations to characterize the energetics and permeability of CO2, O2, and [Formula] through the central pores of two different shell proteins, namely, CsoS1A of -carboxysome and CcmK4 of {beta}-carboxysome shells. We find that the central pores are in fact selectively permeable to anions such as [Formula], as predicted by the model.

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Mahinthichaichan, P., Morris, D. M., Wang, Y., Jensen, G. J., Tajkhorshid, E.. 2018-07-11. Selective Permeability of Carboxysome Shell Pores to Anionic Molecules. https://doi.org/10.1101/367714

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