Promotion of the GTP-liganded state of the Go alpha protein by deletion of the C terminus.

摘要: G proteins are active as long GTP is bound to the alpha subunit. Activation ends when cleaved GDP that then stays site. Agonist-liganded receptors allow formation of state by decreasing affinity subunits for allowing exchange GTP. Since interact with C terminus subunits, we tested whether deletion could mimic activation receptors. Three deletions and one point mutation at o were engineered in cDNA polymerase chain reaction, transcribed into RNA, translated a rabbit reticulocyte lysate. The ability vitro synthesized protein bind guanine nucleotide was inferred from analysis native tryptic cleavage patterns, while associate beta gamma measured sucrose density gradient centrifugation. Deletion 14 amino acids, oD[341], causes large decrease affinity, little or no change guanosine 5'-3-O-(thio)triphosphate affinity. When present, oD[341] remains activated conformation because rapid. 10 oD[345], lowers but less dramatically than oD[341]. 5 oD[350], Arg-349 proline oR[349P] has detectable effects on up acids does not prevent heterotrimers. We propose subunit mobile region blocks dissociation GDP. may move it aside release GDP, GTP,