Some molecular characteristics of human urinary erytopoietin determined by gel filtration and density-gradient ultracentrifugation.

Abstract

Erythropoietin has not yet been isolated in pure form; however, its detectable biologic activity has made possible the study of some of its molecular properties. In this study, gel filtration was combined with density-gradient ultracentrifugation to estimate the molecular radius, sedimentation coefficient, frictional ratio, and molecular weight of human urinary erythropoietin. Gel filtration on Sephadex G-100 columns, calibrated with protein markers of known molecular radii (cytochrome C, ribonuclease, chymotrypsinogen, ovalbumin, and human serum albumin), yielded a molecular radius of 33 A for erythropoietin. Density-gradient ultracentrifugation was performed in a 5 to 15 per cent linear sucrose gradient with radioiodinated serum albumin and ssFe-labeled transferrin added as markers. A sedimentation coefficient of 2.65 was obtained for erythropoietin. Based on these data and if a partial specific volume of 0.70 cm.3 per gram is assumed, the frictional ratio of erythropoietin was calculated to be 1.58 with a molecular weight of 32,600.