Cryo-EM structure of the potassium-chloride cotransporter KCC4 in lipid nanodiscs
Michelle Soto Reid
@SotoReid_M
Michelle S Reid, David M Kern, and Stephen Graf Brohawn
eLife 2020. WEB
En Español, Tagalog
Topology map of KCC4. Structures of KCC4 in lipid nano disc. Ribbon structure of KCC4.
Michelle solved the first K+/Cl- co-transporter structure and probe the functional role of key coordinating residues.
Here are some different ways of thinking about this project…
Big Picture
KCC4 is a protein that helps maintain the cells in your ear healthy and alive. Without KCC4, the cells in your ear shrivel and die off causing you to lose your hearing! For the first time we were able to see what this protein looks like!
Cellular roles
KCC4 is a membrane protein that is important in cellular ion homeostasis. It has many important functions in the different tissues in your body, yet we did not know what it looked like. By understanding how it looks we can design medicine that can help treat diseases.
Medical relevance
KCC4 belongs to the Cation Chloride Co-transporter family (CCCs) which play roles in cellular volume regulation, neural development and function, audition, regulation of blood pressure, and renal function. CCCs are targets of clinically important drugs including loop diuretics and their disruption has been implicated in pathophysiology including epilepsy, hearing loss, and the genetic disorders Andermann, Gitelman, and Bartter syndromes. Here we show the novel structure of KCC4 as a monomer and propose insight into the function and regulation of the transporter family.
Structure Highlights
The cryoEM structure of KCC4 was solved using C1 symmetry to an overall resolution of 3.65 Å. This enabled complete de novo modeling of the transmembrane and extracellular region of KCC4 and includes two partial extracellular glycosylation sites, binding sites for K+ and Cl- ions substrates with ions bound. The discernible density totaled 55.6kDa capturing KCC4 in an inside-open conformation. Importantly, we demonstrate the role of key coordinating residues for transporter activity, and provide a structural explanation for varied substrate specificity and ion transport ratio among CCCs.
David Kern, PhD