Control of inward rectifier K channel activity by lipid tethering of cytoplasmic domains.
Interactions between nontransmembrane domains and the lipid membrane are proposed to modulate activity of many ion channels. In Kir channels, the so-called "slide-helix" is proposed to interact with the lipid headgroups and control channel gating. We examined this possibility directly in a cell-free system consisting of KirBac1.1 reconstituted into pure lipid vesicles. Cysteine substitution of positively charged slide-helix residues (R49C and K57C) leads to loss of channel activity that is rescued by in situ restoration of charge following modification by MTSET(+) or MTSEA(+), but not MTSES(-) or neutral MMTS. Strikingly, activity is also rescued by modification with long-chain alkyl-MTS reagents. Such reagents are expected to partition into, and hence tether the side chain to, the membrane. Systematic scanning reveals additional slide-helix residues that are activated or inhibited following alkyl-MTS modification. A pattern emerges whereby lipid tethering of the N terminus, or C terminus, of the slide-helix, respectively inhibits, or activates, channel activity. This study establishes a critical role of the slide-helix in Kir channel gating, and directly demonstrates that physical interaction of soluble domains with the membrane can control ion channel activity.
Enkvetchakul
Decha
D
Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA. denkvetc@wustl.edu
Jeliazkova
Iana
I
Bhattacharyya
Jaya
J
Nichols
Colin G
CG
D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016957:Burkholderia pseudomallei / Q000235:genetics / Q000378:metabolism*; D002474:Cell-Free System; D003001:Cloning, Molecular; D003545:Cysteine; D005020:Ethyl Methanesulfonate / Q000031:analogs & derivatives / Q000737:chemistry; D015640:Ion Channel Gating; D008563:Membrane Lipids / Q000378:metabolism*; D008698:Mesylates / Q000737:chemistry; D008741:Methyl Methanesulfonate / Q000031:analogs & derivatives / Q000737:chemistry; D008958:Models, Molecular; D009154:Mutation; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012414:Rubidium Radioisotopes; D013439:Sulfhydryl Reagents / Q000737:chemistry
D001426:Bacterial Proteins; D008563:Membrane Lipids; D008698:Mesylates; D024661:Potassium Channels, Inwardly Rectifying; D012414:Rubidium Radioisotopes; D013439:Sulfhydryl Reagents; C093171:methanethiosulfonate ethylammonium; C109153:(2-sulfonatoethyl)methanethiosulfonate; C109154:(2-(trimethylammonium)ethyl)methanethiosulfonate; C014674:methyl methanethiosulfonate; D005020:Ethyl Methanesulfonate; D008741:Methyl Methanesulfonate; D003545:Cysteine
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