Structures and gating mechanisms of the inward rectifier potassium channel Kir7.1
EMSL Project ID
51378
Abstract
Inwardly rectifying K+ (Kir) channels are an important class of K+ channels that conduct K+ ions on hyperpolarization, rather than on depolarization as in other K+ channels. We are using cryo-EM to determine the structure of tetrameric inwardly rectifying potassium (Kir) channel Kir7.1 in incorporated in lipid nanodiscs (MW of tetramer, 160kDa). Our preliminary cryo-EM analysis using a dataset collected on the University of Michigan 200 kV Glacois equipped with a Gatan K2 direct electron detector camera indicates the presence of multiple conformations for the ion channel in this system. Kir7.1 is the most divergent potassium inward rectifier channel in sequence, and its structure has not yet been determined. Kir7.1 channels have several distinct properties and are weak inwardly rectifying channels that facilitate efflux of K+ from cells within the physiological voltage range. This function of Kir7.1 plays a critical role in the retinal pigment epithelium, and mutations in this gene case two forms of human blindness, Snowflake Vitreoretinal Degeneration and Lebers Congenital Amaurosis. Determining the structures in multiple conformational states will contribute to understanding the unique conductance properties of Kir7.1, the fundamental gating mechanisms of the Kir family and provide insight into the molecular basis of an ion channel disease and new opportunities for therapy of such conditions. We are requesting time on Titan Krios time equipped with a Gatan K3 at the PNCC in order to: (1) efficiently collect a large data set of the Kir7.1 ion channel in multiple conformations on a Titan Krios equipped with a Gatan K3 DED with a BioQuantum energy filter, and (2) be able to continue making progress on this project during our extended facility shut-down (our facility is closed from December 2019-June 2020). We have screened vitrified ice grids that are ready for immediate high resolution imaging. Our goal is to improve the resolution of the maps, as well as, determine structures of the Kir7.1 ion channel in multiple conformations.
Project Details
Start Date
2020-05-15
End Date
2021-03-17
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members