Isolation and Partial Characterization of a New Manganoprotein in Soybeans

Abstract

The isolation and partial characterization of a tightly-bound-manganese containing protein in soybean seeds were performed. Sephadex G-lOO rechromatography of the manganese fraction from the aqueous supernatant of soybeans showed one manganese peak corresponding to a molecular weight of 61,000. Upon DEAE-Sephadex A-25 chromatography at pH 7.4, the manganese fraction was separated into two components; component I did not bind to the resin while component II did. Components I and II both contained zinc. The ratio of manganese to zinc contained was about 2 to 1 in both components. Components I and II showed identical absorption spectra with maximum absorption at 278 nm. The molecular weights of the two components were estimated to be the same, 63,000, on SDS–polyacrylamide gel electrophoresis. Component I was found to be a dimer composed of two heterogeneous subunits, with molecular weights of 32,000 and 30,500, on SDS–polyacrylamide gel electrophoresis. Component II was also revealed to be a dimer composed of two heterogeneous subunits, with molecular weights of 32,000 and 31,000.