Fig. 3: The open state of Mrs2.
The cryo-EM density panels refer to the C5 map throughout. a, Left, the 3.2-Å overall resolution cryo-EM density of the CtMrs2 homopentamer open state. Right, cartoon representation of the corresponding structure. The inset shows the feature assigned as cardiolipin, with the equivalent cryo-EM density in gray. b, Surface electrostatics of the open structure shown from the membrane plane, from the intermembrane space and from the matrix. c–f, Structural comparisons of the open and closed CtMrs2 structures along the ion conductance pore at E449-E450 (c; view from the intermembrane space), D420 (d; view from the matrix), M417 (e; view from the intermembrane space) and R413 and R406 (f; view from the intermembrane space). g,h, MOLE and HOLE software analyses of the pore of the open structure, shown as the electrostatic surface, with residues lining the pathway shown as sticks (g) and with the diameter of the pore along the pathway (h). i, Close-up views of the RDLR motif and the R314 wedge in the open structure. j, Putative Mg2+-binding sites at the GMN motif selectivity filter (S site) and at the T427 (P1) and T434 (P2) rings observed in the cryo-EM maps calculated with five-fold symmetry (left) and without symmetry (right). k, Mg2+-binding stoichiometry in various CtMrs2 forms under different conditions, as determined by ICP-MS (stoichiometries refer to Mg2+ per CtMrs2 pentamer). Data points represent the means of five independent measurements, each from one purified sample, and error bars indicate the s.d.
