Hydrodynamic properties of the β adrenergic receptor and adenylate cyclase from wild type and variant S49 lymphoma cells

Cell membranes from clones of cultured S49 mouse lymphoma cells were incubated with [¹²⁵I]iodohydroxybenzyl pindolol, a specific, high affinity ligand for the β-adrenergic receptor, and guanyl-5'-yl imidodiphosphate, which activates adenylate cyclase irreversibly. Membranes were then solubilized with 0.1% Lubrol PX, and hydrodynamic properties of the ligand receptor complex and of adenylate cyclase were determined by gel filtration and by centrifugation through gradients of sucrose in H₂O or D₂O. Molecular parameters for the β-adrenergic receptor from wild type cells are: Stokes radius, 6.4 nm; s(20.w), 3.1 S; partial specific volume, 0.83 ml/g; M(r), 130,000; frictional ratio, 1.8. The values for adenylate cyclase are: Stokes radius, 7.1 nm; s(20.w), 7.5 S; partial specific volume, 0.78 ml/g; M(r), 270,000; frictional ratio, 1.6. Essentially identified results were obtained with preparations from a variant clone in which the receptor and adenylate cylcase are permanently uncoupled and for the β-adrenergic receptor in a clone that lacks adenylate cyclase activity. The amounts of detergent that are estimated to be bound to the receptor and to adenylate cyclase are 0.8 and 0.2 mg/mg of protein, respectively, assuming that the partial specific volume observed represents the weight average for protein and for Lubrol PX. Values of M(r) for the protein are then calculated to be 75,000 for the β-adrenergic receptor and 220,000 for adenylate cyclase.