Comparative studies on fraction 1 protein from spinach and tobacco leaves

Fraction 1 protein of spinach and tobacco leaves was purifiedby Sephadex G-200 and DEAE-cellulose column chromatography.Immunological comparison of purified preparations of these proteinswas carried out with precipitin analysis using an antiserumof tobacco fraction 1 protein. Two different antigenic activitieswere found in tobacco fraction 1 protein, of which one was commonlyfound in the spinach protein and the other was specific to tobaccofraction 1 protein. The immunological results suggest that fraction 1 protein iscomposed of at least two different structures, one of whichis common to both spinach and tobacco proteins and the otherof which is specific to each of these proteins. This was confirmedfrom a chemical experiment. Fraction 1 protein was divided intolarge and small polypeptide components by sodium dodecyl sulfatetreatment and subsequent Sephadex G-100 column chromatography,then the amino acid compositions of each polypeptide of theseproteins were compared. The amino acid composition of the smallpolypeptide of spinach was different from that of tobacco, whileamino acid compositions of the large polypeptides of those proteinswere similar to each other. (Received July 1, 1968; )