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Kv4.2 Potassium Voltage-Gated Ion Channel Electron Microscopy Data
Kv4.2 Potassium Voltage-Gated Ion Channel
Regulatory KChIP2 subunits assemble with pore-forming Kv4.2 subunits in 4:4 complexes to produce native voltage-gated potassium (Kv) channels like cardiac I(to) and neuronal I(A) subtypes. Here, negative stain electron microscopy (EM) and single particle averaging reveal KChIP2 to create a novel approximately 35 x 115 x 115 Angstrom, intracellular fenestrated rotunda: four peripheral columns that extend down from the membrane-embedded portion of the channel to enclose the Kv4.2 "hanging gondola" (a platform held beneath the transmembrane conduction pore by four internal columns). To reach the pore from the cytosol, ions traverse one of four external fenestrae to enter the rotundal vestibule and then cross one of four internal windows in the gondola.
Linked to the right is a stack (257 MB) of 8,314 images (MRC/CCP4 format ) of Kv4.2 potassium voltage-gated ion channel . The images were recorded with a Philips CM12 electron microscope at an acceleration voltage of 120 keV, at 1.5 µm underfocus and a magnification of 60,000x. Micrographs were scanned with a step size of 28 µm, giving a pixel size of 4.67 Å on the specimen. Alignment parameters determined by Frealign for each particle in the stack can also be found below, as well as a reconstruction of Kv4.2 (also MRC/CCP4 format; a B-factor of -5000.0 Å2 and 28.0 Å low-pass filter radius were applied using the program bfactor to sharpen the density) and a script to calculate a reconstruction using Frealign.
Please note that the handedness of the reconstruction calculated using the attached parameter files will be WRONG. The reconstruction must be mirrored (for example, with the MRC program label) to have the correct handedness. The reconstruction attached below has already been corrected.