Electrophoretic Patterns of Soluble Proteins in Tobacco Leaf During Curing

Polyacrylamide gel disc electrophoresis revealed at least 13 anodic protein bands in leaf extracts of seven tobacco (Nicotiana tabacum L.) strains representing Burley, Turkish, flue- and fire-cured types. Four major bands B, E, G, and J were common in all strains. Weak bands varied slightly in mobility and in number among tobacco types. Studies of cell fractions of Burley 21 leaves yielded information that bands A, C, D, G, and J are present in the cytoplasm, whereas all but bands B, E, L, and M appeared to be identical in the chloroplast, mitochondrial, and nuclear extracts. The resemblance in protein banding pattern among the organelles indicates similarity in their membrane proteins. Bands B, E, L, and M are associated with plasma membrane or cell wall. During simulated air-curing, a majority of bands diminished by the tenth day, whereas bands B, E, and G remained highly intense and the concentration of band C was reduced in cured leaves. Bands B, E, and G reacted positively with the periodic-acid Schiff's reagent (PAS) but negatively with the colloidal ion staining. Trypsin digestion abolished protein bands stained with amido black or the PAS reagent. Results suggest that bands B, E, and G are neutral or weakly acidic glycoproteins