| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 1998: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1997: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
Voltage-gated potassium channels are macromolecular pores, which permit the trans-membrane flux of potassium ions. Most potassium channels enter the inactivated states, which do not permit the permeation of ions. In this study, molecular mechanisms of the inactivation were examined on some cloned voltage-gated potassium channels (two Aplysia channels, aKvl.la & aKv5.1, and a rat channel, rKvl.4). aKvl.la and rKvl.4 are homologous channels, and both channels show a prominent inactivation called the accumulative inactivation. When the channel currents were examined in inside-out patches, however, these two channels showed a remarkable contrast ; the accumulative inactivation of aKvl.la was enhanced, while that of rKviL4 depressed. There are some evidence which suggest the involvement of pore structure in the accumulative inactivation, and indeed, in the pore region of the channels, 8 amino acids are different between aKvl.la and rKvl.4. Therefore, eight pore mutants of aKvl.la were made, and the effects of each mutation were examined in Xenopus oocyte expression system. The results suggest that the difference of the accumulative inactivation of aKvl.la and rKvl.4 is due to the different structure of the external mouth of the pore. To confirm the results in the channels that lack N-type inactivation, the amino-terminal deletion mutants of the eight mutants were made. The functional consequence of such deletion on the accumulative inactivation is currently under investigation. Because aKv5.1 lacks the inactivation at all, we are now trying to examine the chimera channels between aKvl.la and aKv5.1 to delineate the important domains for the inactivation.
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