期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1998
卷号：95
期号：24
页码：14546-14551
DOI：10.1073/pnas.95.24.14546
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Native cylic nucleotide-gated (CNG) channels are composed of and {beta} subunits. Olfactory CNG channels were expressed from rat cDNA clones in Xenopus oocytes and studied in inside-out patches. Using tandem dimers composed of linked subunits, we investigated the stoichiometry and arrangement of the and {beta} subunits. Dimers contained three subunit types: wt, {beta}wt, and m. The m subunit lacks an amino-terminal domain that greatly influences gating, decreasing the apparent affinity of the channel for ligand by 9-fold, making it a reporter for inclusion in the tetramer. Homomeric channels from injection of wtwt dimers and from wt monomers were indistinguishable. Channels from injection of wtm dimers had apparent affinities 3-fold lower than wt homomultimers, suggesting a channel with two wt and two m subunits. Channels from coinjection of wtwt and {beta}{beta} dimers were indistinguishable from those composed of and {beta} monomers and shared all of the characteristics of the +{beta} phenotype of heteromeric channels. Coinjection of wtm and {beta}{beta} dimers yielded channels also of the +{beta} phenotype but with an apparent affinity 3-fold lower, indicating the presence of m in the tetramer and that +{beta} channels have adjacent -subunits. To distinguish between an ---{beta} and an --{beta}-{beta} arrangement, we compared apparent affinities for channels from coinjection of wtwt and {beta}wt or wtwt and {beta}m dimers. These channels were indistinguishable. To further argue against an ---{beta} arrangement, we quantitatively compared dose-response data for channels from coinjection of wtm and {beta}{beta} dimers to those from and {beta} monomers. Taken together, our results are most consistent with an --{beta}-{beta} arrangement for the heteromeric olfactory CNG channel.
