5kum
From Proteopedia
Crystal Structure of Inward Rectifier Kir2.2 K62W Mutant In Complex with PIP2
Structural highlights
Function[KCJ12_CHICK] Inward rectifying potassium channel that is activated by phosphatidylinositol 4,5-bisphosphate and that probably participates in controlling the resting membrane potential in electrically excitable cells. Inward rectifier potassium channels are characterized by a greater tendency to allow potassium to flow into the cell rather than out of it. The inward rectification is probably due to the blockage of outward current by cytoplasmic polyamines and/or magnesium ions.[1] [2] Publication Abstract from PubMedInward rectifier potassium (Kir) channel activity is controlled by plasma membrane lipids. Phosphatidylinositol-4,5-bisphosphate (PIP2) binding to a primary site is required for opening of classic inward rectifier Kir2.1 and Kir2.2 channels, but interaction of bulk anionic phospholipid (PL(-)) with a distinct second site is required for high PIP2 sensitivity. Here we show that introduction of a lipid-partitioning tryptophan at the second site (K62W) generates high PIP2 sensitivity, even in the absence of PL(-) Furthermore, high-resolution x-ray crystal structures of Kir2.2[K62W], with or without added PIP2 (2.8- and 2.0-A resolution, respectively), reveal tight tethering of the C-terminal domain (CTD) to the transmembrane domain (TMD) in each condition. Our results suggest a refined model for phospholipid gating in which PL(-) binding at the second site pulls the CTD toward the membrane, inducing the formation of the high-affinity primary PIP2 site and explaining the positive allostery between PL(-) binding and PIP2 sensitivity. Structural basis of control of inward rectifier Kir2 channel gating by bulk anionic phospholipids.,Lee SJ, Ren F, Zangerl-Plessl EM, Heyman S, Stary-Weinzinger A, Yuan P, Nichols CG J Gen Physiol. 2016 Sep;148(3):227-37. doi: 10.1085/jgp.201611616. Epub 2016 Aug , 15. PMID:27527100[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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