Detection of the expression and function of m3AChR-G11 fusion protein

Aim To generate m3AChR-G11 fusion protein in baculovirus-Sf9 cells and test the couping function,the interation and the influence factors be-tween m3AChR and G11 protein,as well as screen the specific ligands for m3AChR. Methods m3AChR-G11 fused DNA was generated through a two-step PCR and then expressed in Sf9 cells to produce fusion protein. The total concentration for membrane protein was de-tected by BCA method,[3H]QNB and [35 S]GTPγS binding experiment as perfomed to study the function of m3AChR-G11 fusion protein. Results The expression level of m3AChR-G11 was 7. 76 × 10 -9 mol·g -1. The affinity of GDP to G11 partner changed in the presence of different muscarinic ligands. IC50 values of GDP in the presence of ACh,Pilo,CCh,MCN-A-343,Atro,4-Damp and Dafi were 82. 2,93. 70,12. 10,14. 30, 1. 93,1. 37,0. 72 × 10 -6 mol · L -1 respectively,and that in the absence of muscarinic was 1. 99 × 10 -6 mol ·L-1.Concluslons The m3AChR-G11 fusion protein has the pharmacological specificity of m3 receptor and the efficient coupling interaction of the two partners. Affinity of GDP to ligand-bound fusion protein represents the species of muscarinic ligands. This is helpful in screening and detecting the new specific ligands to muscarinic receptors.