RT Journal Article
SR Electronic
T1 Selective Permeability of Carboxysome Shell Pores to Anionic Molecules
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 367714
DO 10.1101/367714
A1 Paween Mahinthichaichan
A1 Dylan M. Morris
A1 Yi Wang
A1 Grant J. Jensen
A1 Emad Tajkhorshid
YR 2018
UL http://biorxiv.org/content/early/2018/07/11/367714.abstract
AB 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 (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 through the central pores of two different shell proteins, namely, CsoS1A of α–carboxysome and CcmK4 of β-carboxysome shells. We find that the central pores are in fact selectively permeable to anions such as , as predicted by the model.