Isolation and purification of a low molecular weight protein from bovine urine

A low molecular weight protein was separated from urine samples obtained from a heifer with spontaneous renal disease and from cows with CaNa2EDTA-induced renal dysfunction. The molecular weight and electrophoretic mobility of the separated protein were examined. The low molecular weight protein collected by gel filtration chromatography was further separated into two fractions by ion exchange chromatography using DEAE-cellulose. One of the two fractions, the lowest molecular weight protein showed a single band in SDS-PAGE, and its molecular weight was approximately 12,000. An antiserum against this protein formed a single precipitin line with the urine from cows with experimentally induced renal dysfunction and a heifer with spontaneous renal disease by the double immunodiffusion technique. However, the antiserum did not form any precipitin line with the concentrated urine of healthy cow and human beta 2-microglobulin. In cellulose acetate membrane electrophoresis, this protein migrated in the same position as that of serum gamma-globulin from healthy cow.