http://www.jgp.org The Journal of General Physiology RSS feed -- recent COMMUNICATION articles 1540-7748 The Journal of General Physiology 0022-1295 http://www.jgp.org/icons/banner/title.gif http://www.jgp.org http://www.jgp.org/cgi/content/short/130/3/329?rss=1 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.

]]> 2007-08-27 info:doi/10.1085/jgp.200709764 The Rockefeller University Press 3 130 334 2007-08-27 329 COMMUNICATION