Flexibility of the Kir6.2 inward rectifier K(+) channel pore. Export

@article{citeulike:5969050, abstract = {Interactions of sulfhydryl reagents with introduced cysteines in the pore-forming (Kir6.2) subunits of the K(ATP) channel were examined. 2-Aminoethyl methanethiosulfonate (MTSEA(+)) failed to modify Cd(2+)-insensitive control-Kir6.2 channels, but rapidly and irreversibly modified Kir6.2[L164C] (L164C) channels. Although a single Cd(2+) ion is coordinated by L164C, four MTSEA(+) "hits" can occur, each sequentially reducing the single-channel current. A dimeric fusion of control-Kir6.2 and L164C subunits generates Cd(2+)-insensitive channels, confirming that at least three cysteines are required for coordination, but MTSEA(+) modification of the dimer occurs in two hits. L164C channels were not modified by bromotrimethyl ammoniumbimane (qBBr(+)), even though qBBr(+) caused voltage-dependent block (as opposed to modification) that was comparable to that of MTSEA(+) or 3-(triethylammonium)propyl methanethiosulfonate (MTSPTrEA(+)), implying that qBBr(+) can also enter the inner cavity but does not modify L164C residues. The Kir channel pore structure was modeled by homology with the KcsA crystal structure. A stable conformation optimally places the four L164C side chains for coordination of a single Cd(2+) ion. Modification of these cysteines by up to four MTSEA(+) (or three MTSPTrEA(+), or two qBBr(+)) does not require widening of the cavity to accommodate the derivatives within it. However, like the KcsA crystal structure, the energy-minimized model shows a narrowing at the inner entrance, and in the Kir6.2 model this narrowing excludes all ions. To allow entry of ions as large as MTSPTrEA(+) or qBBr(+), the entrance must widen to >8 A, but this widening is readily accomplished by minimal M2 helix motion and side-chain rearrangement.}, author = {Loussouarn, G. and Phillips, L. R. and Masia, R. and Rose, T. and Nichols, C. G.}, citeulike-article-id = {5969050}, citeulike-linkout-0 = {http://dx.doi.org/10.1073/pnas.061452698}, citeulike-linkout-1 = {http://view.ncbi.nlm.nih.gov/pubmed/11274446}, citeulike-linkout-2 = {http://www.hubmed.org/display.cgi?uids=11274446}, day = {27}, doi = {10.1073/pnas.061452698}, issn = {0027-8424}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, keywords = {katp, kir62, pore}, month = {March}, number = {7}, pages = {4227--4232}, posted-at = {2009-10-19 06:07:17}, priority = {2}, title = {Flexibility of the Kir6.2 inward rectifier K(+) channel pore.}, url = {http://dx.doi.org/10.1073/pnas.061452698}, volume = {98}, year = {2001} }

TY - JOUR ID - citeulike:5969050 L3 - citeulike-article-id:5969050 N2 - Interactions of sulfhydryl reagents with introduced cysteines in the pore-forming (Kir6.2) subunits of the K(ATP) channel were examined. 2-Aminoethyl methanethiosulfonate (MTSEA(+)) failed to modify Cd(2+)-insensitive control-Kir6.2 channels, but rapidly and irreversibly modified Kir6.2[L164C] (L164C) channels. Although a single Cd(2+) ion is coordinated by L164C, four MTSEA(+) "hits" can occur, each sequentially reducing the single-channel current. A dimeric fusion of control-Kir6.2 and L164C subunits generates Cd(2+)-insensitive channels, confirming that at least three cysteines are required for coordination, but MTSEA(+) modification of the dimer occurs in two hits. L164C channels were not modified by bromotrimethyl ammoniumbimane (qBBr(+)), even though qBBr(+) caused voltage-dependent block (as opposed to modification) that was comparable to that of MTSEA(+) or 3-(triethylammonium)propyl methanethiosulfonate (MTSPTrEA(+)), implying that qBBr(+) can also enter the inner cavity but does not modify L164C residues. The Kir channel pore structure was modeled by homology with the KcsA crystal structure. A stable conformation optimally places the four L164C side chains for coordination of a single Cd(2+) ion. Modification of these cysteines by up to four MTSEA(+) (or three MTSPTrEA(+), or two qBBr(+)) does not require widening of the cavity to accommodate the derivatives within it. However, like the KcsA crystal structure, the energy-minimized model shows a narrowing at the inner entrance, and in the Kir6.2 model this narrowing excludes all ions. To allow entry of ions as large as MTSPTrEA(+) or qBBr(+), the entrance must widen to >8 A, but this widening is readily accomplished by minimal M2 helix motion and side-chain rearrangement. IS - 7 JF - Proceedings of the National Academy of Sciences of the United States of America SN - 0027-8424 EP - 4232 TI - Flexibility of the Kir6.2 inward rectifier K(+) channel pore. VL - 98 SP - 4227 KW - katp KW - kir62 KW - pore AU - Loussouarn, G AU - Phillips, LR AU - Masia, R AU - Rose, T AU - Nichols, CG PY - 2001/03/27/ UR - http://dx.doi.org/10.1073/pnas.061452698 ER -