A MOLYBDENUM COFACTOR-CONTAINING PROTEIN FROM PISUM-SATIVUM L - ISOLATION AND PURIFICATION FROM PEA-SEEDS

A novel protein containing a molybdenum cofactor has been isolated and purified to electrophoretic homogeneity from pea seeds. The purificat ion procedure includes ammonium sulfate fractionation, ion-exchange ch romatography on DEAE-Toyopearl 650 M, gel filtration on Sephacryl S-20 0, and covalent chromatography on Thiol-Sepharose 4B. The protein was partially characterized and shown to have isoelectric point at pH 5.0, molecular mass of 300 kD, and dimeric structure with two identical su bunits of molecular mass 150 kD. The absorption spectrum of the protei n indicates the absence of chromophoric groups. The molybdenum cofacto r is tightly bound to the protein and can be detected by its reaction with a deficient nitrate reductase from the nit-1 mutant of Neurospora crassa only after heating of the preparation. A unique quality of the purified protein is the absence of molybdenum in the structure of the cofactor.