(
A) Sequence alignment of the putative pore helix of Venus flytrap FLYC1 and Drosera DcFLYC1.1 and DcFLYC1.2 proteins with MSL10 and MscS. Nonpolar, polar, and ionizable residues are orange, light blue, and dark blue, respectively. A glycine predicted to localize at a central bend in the helix is shaded green. (
B) Modeled heptameric organization. The sequence of Venus flytrap FLYC1 was threaded on the inner helix of heptameric MscS in a closed conformation (PDB 2OAU), and minimized using the Rosetta energy function while imposing C
7 symmetry. Subunits are shown in different colors. Basic residues K558 and K579 are green and purple sticks, respectively. Predicted intersubunit hydrogen bonds between serines S564 and S565 (light blue sticks) of pore segments are shown with red dashes, while a ring of phenylalanines (F572; orange spheres) constrict the pore. Helices TM6a, forming the central pore, and amphipathic helix TM6b are indicated for one pore segment. (
C) A cross-section through the protein surface colored by electrostatic potential, showing an uncharged (white) pore, with positive charge (blue) above and below the pore. (
D) Average I–V of stretch-activated single-channel currents from
FLYC1 (N=7) and
FLYC1(K579E) (N=4) in asymmetrical NaCl solution.
FLYC1 data is the same as
Figure 4D. Scatter plots are mean ± s.e.m.