Characterization of Deletion and Truncation Mutants of the Rat Glucagon Receptor: SEVEN TRANSMEMBRANE SEGMENTS ARE NECESSARY FOR RECEPTOR TRANSPORT TO THE PLASMA MEMBRANE AND GLUCAGON BINDING (*)

摘要: Glucagon receptor mutants were characterized with the aim of elucidating minimal structural requirements for proper biosynthesis, ligand binding, and adenylyl cyclase coupling. One N-terminal deletion mutant five truncation progressively shorter C termini expressed in transiently transfected monkey kidney (COS-1) cells. Each was designed so that truncated C-terminal tail would remain on cytoplasmic surface receptor. In order to characterize cellular location mutants, a highly specific, high affinity antipeptide antibody prepared against extracellular, Immunoblot analysis immunofluorescence microscopy showed presence all seven putative transmembrane segments, but not an intact tail, required cell expression Membranes from cells expressing lacking large portion or any segments failed bind glucagon. which retained bound glucagon affinities similar native activated response These results indicate helices are necessary folding processing Glycosylation is reach surface, it may be binding. However, extracellular Most distal absence increase slightly binding The also coupling therefore does play direct role G protein (GS) activation by