Abstract:
:We expressed rod-type homotetrameric cyclic nucleotide-gated (CNGA1) channels in Xenopus oocytes and studied activation by photolysis-induced jumps of the 3',5'-cyclic guanosine monophosphate (cGMP) concentration and by voltage steps. cGMP jumps to increasing concentrations up to the EC50 value of 46.5 microM decelerate the activation gating, indicative that even at concentrations of cGMP < EC50 binding is not rate limiting. Above the EC50 value, activation by cGMP jumps is again accelerated to the higher concentrations. At the same cGMP concentration, the speed of the activation gating by depolarizing voltage steps is roughly similar to that by cGMP jumps. Permeating ions passing the pore more slowly (Rb+ > K+ > Na+) slow down the activation time course. At the single-channel level, cGMP jumps to high concentrations cause openings directly to the main open level without passing sublevels. From these results it is concluded that at both low and high cGMP the gating of homotetrameric CNGA1 channels is not rate-limited by the cGMP binding but by conformational changes of the channel which are voltage dependent and include movements in the pore region.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Nache V,Kusch J,Hagen V,Benndorf Kdoi
10.1529/biophysj.105.078667subject
Has Abstractpub_date
2006-05-01 00:00:00pages
3146-54issue
9eissn
0006-3495issn
1542-0086pii
S0006-3495(06)72496-1journal_volume
90pub_type
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