Molecular Weight of Detergent-Solubilized Prostaglandin-F2alpha Receptor from Bovine Corpora Lutea

Abstract

A prostaglandin F_2α receptor localized in plasma membranes of bovine corpus luteum cells was solubilized by treatment with Triton X‐100. Sepharose chromatographies of ([³H]prostaglandin F_2α)‐receptor complex gave a Stokes' radius of 630 nm. In the absence of detergent, aggregated forms of the receptor appeared. Sedimentation experiments of solubilized receptor in sucrose/H₂O and sucrose/²H₂O density gradients gave the following values: sedimentation coefficient (s_{20, w}) 4.6 S; partial specific volume (ν_B) 0.78 cm³/g and frictional ratio (f/f₀) 1.6. Based on the sedimentation coefficient and the Stokes' radius and assuming that the receptor is a non‐glycosylated protein the molar mass of the receptor‐(Triton X‐100) complex was 144000 g/mol. The ν_B value indicated that ca. 26% of the weight represented bound detergent and that the molecular weight of the prostaglandin F_2α receptor is approximately 107000.