The transmembrane topology of the amino terminus of the alpha subunit of the nicotinic acetylcholine receptor.

摘要: We have investigated the transmembrane topology of amino-terminal domain alpha subunit mouse muscle nicotinic acetylcholine receptor synthesized in vitro and vivo. Using oligonucleotide-directed mutagenesis we introduced new glycosylation consensus sequences at 154 200. For each novel site, additional constructs were made which original site N141 was eliminated. Glycosylation sites, as exhibited a rabbit reticulocyte cell-free translation system supplemented with canine pancreatic microsomes transient transfection COS cells, taken evidence translocation site. Each sites glycosylated both systems. In separate experiments found that an fragment terminating M207 could be extracted from microsomal membranes sodium carbonate after translation, indicating this is not integral membrane protein. Our results, together previous experiments, indicate amino terminus up to least residue 207 translocated across endoplasmic reticulum. This probably represents orientation assembled receptor.