Molecular Weight of Human Renin. ∗

Abstract

Whitaker first noted a linear correlation between the logarithm of the molecular weight of a protein and the ratio of its elution volume to the column void volume using G-75 and G-100 Sephadex (1). This work was extended by several investigators using G-75, G-100 and/or G-200 Sephadex to determine the molecular weights of proteins ranging from 13,000 to 225,000(2,3).

As renin has not been obtained in pure form, classical molecular weight (m.w.) determinations have not been possible. However, with the introduction of gel-filtration it proved possible to determine the molecular weight of a protein in a crude preparation (3). Gel-filtration has already been applied to hog renin, which had an elution volume between that of ¹²⁵I labelled human albumin (m.w. 69,000) and pepsin (m.w. 35,000) and was estimated as having a molecular weight between 42,000 and 49,000(4). The present study applied the method of Whitaker (1) toward the determination of the molecular weight of human renin.

Methods. Proteins of known molecular weight. Thyroglobulin: porcine, water soluble, lot 1923-60. Catalase: beef liver, slightly soluble, lot 45B-0440. Gamma-globulin: bovine, Cohn fraction II, lot 15B-2920. Serum albumin: human, grade III, lot 65B-1630. Ovalbumin: grade V, lot A102B-250. Pepsin: 2X crystallized, lot 15B-1370. All proteins used were obtained from the Sigma Chemical Co., St. Louis, Mo, Human renin. The dog unit (DU) of renin is defined as that quantity of renin required to raise the mean femoral blood pressure of an unanesthetized dog by 30 mm Hg(5). Renin, of a specific activity of 0.5 DU/mg protein was prepared from fresh-frozen human kidneys by the method of Dexter, Haynes and Bridges(6), followed by lyophilization and gel filtration on G-75 Sephadex. Final preparations were lyophilized and stored until used.