Inner and Outer Coordination Shells of Mg<sup>2+</sup> in CorA Selectivity
Filter from Molecular Dynamics Simulations
Sunan Kitjaruwankul
Pattama Wapeesittipan
Panisak Boonamnaj
Pornthep Sompornpisut
10.1021/acs.jpcb.5b10925.s001
https://acs.figshare.com/articles/journal_contribution/Inner_and_Outer_Coordination_Shells_of_Mg_sup_2_sup_in_CorA_Selectivity_Filter_from_Molecular_Dynamics_Simulations/2081080
Structural data of CorA Mg<sup>2+</sup> channels show that the
five Gly-Met-Asn (GMN) motifs at the periplasmic loop of the pentamer
structure form a molecular scaffold serving as a selectivity filter.
Unfortunately, knowledge about the cation selectivity of Mg<sup>2+</sup> channels remains limited. Since Mg<sup>2+</sup> in aqueous solution
has a strong first hydration shell and apparent second hydration sphere,
the coordination structure of Mg<sup>2+</sup> in a CorA selectivity
filter is expected to be different from that in bulk water. Hence,
this study investigated the hydration structure and ligand coordination
of Mg<sup>2+</sup> in a selectivity filter of CorA using molecular
dynamics (MD) simulations. The simulations reveal that the inner-shell
structure of Mg<sup>2+</sup> in the filter is not significantly different
from that in aqueous solution. The major difference is the characteristic
structural features of the outer shell. The GMN residues engage indirectly
in the interactions with the metal ion as ligands in the second shell
of Mg<sup>2+</sup>. Loss of hydrogen bonds between inner- and outer-shell
waters observed from Mg<sup>2+</sup> in bulk water is mostly compensated
by interactions between waters in the first solvation shell and the
GMN motif. Some water molecules in the second shell remain in the
selectivity filter and become less mobile to support the metal binding.
Removal of Mg<sup>2+</sup> from the divalent cation sensor sites of
the protein had an impact on the structure and metal binding of the
filter. From the results, it can be concluded that the GMN motif enhances
the affinity of the metal binding site in the CorA selectivity filter
by acting as an outer coordination ligand.
2016-01-28 00:00:00
selectivity filter
Outer Coordination Shells
GMN motif
Mg
bulk water
MD
CorA Selectivity Filter
pentamer structure form
Molecular Dynamics SimulationsStructural data
CorA selectivity filter
divalent cation sensor sites
metal binding
metal binding site