Avtor/Urednik		Rothwell, Simon W.; Stansfeld, Phillip J.; Bragg, Laricia; Verkhratsky, Alexei; North, Alan R.
Naslov		Direct gating of ATP-activated ion channels (P2X2 receptors) by lipophilic attachment at the outer end of the second transmembrane domain
Tip		članek
Vol. in št.		Letnik 289, št. 2
Leto izdaje		2014
Obseg		str. 618-626
ISSN		0021-9258 - The Journal of biological chemistry
Jezik		eng
Abstrakt		The ionic pore of the P2X receptor passes through the central axis of six transmembrane (TM) helices, two from each of three subunits. Val48 and Ile328 are at the outer end of TM1 and TM2, respectively. Homology models of the open and closed states of P2X2 indicate that pore opening is associated with a large lateral displacement of Ile328. In addition, molecular dynamics simulations suggest that lipids enter the interstices between the outer ends of the TM domains. The P2X2(I328C) receptor was activated by propyl-methanethiosulfonate (MTS) as effectively as by ATP, but cysteine substitutions elsewhere in TM2 had no such effect. Other lipophilic MTS compounds (methyl, ethyl, and tert-butylethyl) had a similar effect but not polar MTS. The properties of the conducting pathway opened by covalent attachment of propyl-MTS were the same as those opened by ATP, with respect to unitary conductance, rectification, and permeability of N-methyl-d-glucamine. The ATP-binding residue Lys69 was not required for the action of propyl-MTS, although propyl-MTS did not open P2X2(K308A/I328C) receptors. The propyl-MTS did not open P2X2 receptors in which the Val48 side chain was removed (P2X2(V48G/I328C)). The results suggest that an interaction between Val48 and Ile328 stabilizes the closed channel and that this is broken by covalent attachment of a larger lipophilic moiety at the I328C receptors. Lipid intercalation between the separating TM domains during channel opening would be facilitated in P2X2(I328C) receptors with attached propyl-MTS. The results are consistent with the channel opening mechanism proposed on the basis of closed and open crystal structures and permit the refinement of the position of the TMs within the bilayer.
Proste vsebinske oznake		ion channels lipophilic MTS compounds receptor permeation ionski kanali lipofilne MTS spojine receptor prepustnosti