Hydrodynamic characterization of the Triton X-100 solubilized lactogenic hormone receptor of rat liver

Rat liver plasma membranes, prelabeled with radioactive human growth hormone, were extracted with Triton X-100. The solubilized lactogenic hormone receptor had a Stokes radius of 54.2 A on Sepharose 6B chromatography. Numerical integration of the results of sedimentation experiments on the solubilized hormone-receptor-Triton X-100 complex in sucrose/H2O and sucrose/2H2O density gradients produced an s20,w = 5.05 X 10(-13) S and a partial specific volume of 0.791 cm3 g-1. From these data a molecular weight of 148 000 and frictional ratio of 1.40 for the hormone-receptor-Triton X-100 complex were calculated. Triton X-100 was calculated to comprise 32.4% of the complex, and thus, the hormone-receptor complex has a molecular weight of 99 800. These results indicate that the lactogenic hormone receptor, as would be expected of an integral membrane protein, has the capacity to bind a large amount of detergent.