TY - JOUR
T1 - The polyamine binding site in inward rectifier K+ channels
AU - Kurata, Harley T.
AU - Marton, Laurence J.
AU - Nichols, Colin G.
PY - 2006/5
Y1 - 2006/5
N2 - Strongly inwardly rectifying potassium channels exhibit potent and steeply voltage-dependent block by intracellular polyamines. To locate the polyamine binding site, we have examined the effects of polyamine blockade on the rate of MTSEA modification of cysteine residues strategically substituted in the pore of a strongly rectifying Kir channel (Kir6.2[N160D]). Spermine only protected cysteines substituted at a deep location in the pore, between the "rectification controller" residue (N160D in Kir6.2, D172 in Kir2.1) and the selectivity filter, against MTSEA modification. In contrast, blockade with a longer synthetic polyamine (CGC-11179) also protected cysteines substituted at sites closer to the cytoplasmic entrance of the channel. Modification of a cysteine at the entrance to the inner cavity (169C) was unaffected by either spermine or CGC-11179, and spermine was clearly "locked" into the inner cavity (i.e., exhibited a dramatically slower exit rate) following modification of this residue. These data provide physical constraints on the spermine binding site, demonstrating that spermine stably binds at a deep site beyond the "rectification controller" residue, near the extracellular entrance to the channel.
AB - Strongly inwardly rectifying potassium channels exhibit potent and steeply voltage-dependent block by intracellular polyamines. To locate the polyamine binding site, we have examined the effects of polyamine blockade on the rate of MTSEA modification of cysteine residues strategically substituted in the pore of a strongly rectifying Kir channel (Kir6.2[N160D]). Spermine only protected cysteines substituted at a deep location in the pore, between the "rectification controller" residue (N160D in Kir6.2, D172 in Kir2.1) and the selectivity filter, against MTSEA modification. In contrast, blockade with a longer synthetic polyamine (CGC-11179) also protected cysteines substituted at sites closer to the cytoplasmic entrance of the channel. Modification of a cysteine at the entrance to the inner cavity (169C) was unaffected by either spermine or CGC-11179, and spermine was clearly "locked" into the inner cavity (i.e., exhibited a dramatically slower exit rate) following modification of this residue. These data provide physical constraints on the spermine binding site, demonstrating that spermine stably binds at a deep site beyond the "rectification controller" residue, near the extracellular entrance to the channel.
UR - http://www.scopus.com/inward/record.url?scp=33646122685&partnerID=8YFLogxK
U2 - 10.1085/jgp.200509467
DO - 10.1085/jgp.200509467
M3 - Article
C2 - 16606689
AN - SCOPUS:33646122685
SN - 0022-1295
VL - 127
SP - 467
EP - 480
JO - Journal of General Physiology
JF - Journal of General Physiology
IS - 5
ER -