The Size of Adenylate Cyclase

作者：Eva J. Neer · 发表于：Journal of Biological Chemistry · 年份：1974 · DOI：10.1016/s0021-9258(19)42188-1 · 被引用次数：122 · 研究领域：Biomedical Research and Pathophysiology、Ion Transport and Channel Regulation、Hemoglobin structure and function

Abstract Adenylate cyclase from the rat renal medulla has been solubilized with the nonionic detergents Triton X-100 and Lubrol PX. The enzyme activity in a 100,000 x g Lubrol PX supernatant is resolved into three peaks by gel filtration on Sepharose 4B: Peak A in the void volume; Peak B, the major form, with a Stokes radius of 64 A; and Peak C with a Stokes radius of 34 A. When Triton X-100 is used to solubilize the enzyme activity is only found at the positions of Peaks B and C and the Stokes radii are 62 A and 28 A, respectively. The sedimentation coefficients for the two smaller forms have been determined by centrifugation in 5 to 20 % sucrose gradients. By comparing sedimentation of activity in sucrose gradients made up in H2O and D2O, the partial specific volume (v) of the predominant form (Peak B) was estimated. The molecular properties of the predominant form of adenylate cyclase in Triton X-100 are: s20,w, 5.9 S; v, 0.74 ml per g; mass, 159,000 daltons; f:f0, 1.6. For the minor form, the values are: s20,w, 3.0 S; mass, 38,000 daltons, f:f0, 1.2. The partial specific volume of the smaller species was assumed to be the same as the larger. The corresponding values determined in Lubrol PX are similar. The low value for v obtained in these studies suggests that adenylate cyclase binds very little detergent, less than 0.2 mg of detergent per mg of protein. Since interactions with detergents probably substitute for interactions with lipids and hydrophobic amino acid side ch...