Partial Purification and Preliminary Characterization of Soluble Leaf Proteins Specific to Virus Infected Tobacco Plants

The' b' protein components specific to virus infected tobacco leaves (Gianinazzi, Martin & Vall~e, 197o) can be partially purified by preferential extraction at pH 2.8. Evidence is presented that they are rich in aromatic amino acids. Results of treatment of the proteins with SDS and subsequent separation by gel electrophoresis in the presence of SDS suggest that b~, b~ and b~ are composed of the same monomer of mol. wt. about 16000 whilst b4 is composed of a monomer of tool. wt. about 29ooo. By purifying and concentrating the soluble protein extracts of water inoculated leaves, further evidence is provided that the 'b ' proteins are not normal constituents of healthy tobacco leaves.