Identification of a 220 kDa membrane-associated plant cell protein immunologically related to human beta-spectrin.

Electrophoretic analysis of low ionic strength extracts of tomato plant leaves revealed the presence of two proteins of apparent molecular weights of 240 kDa and 220 kDa which co-migrated with purified human erythrocyte alpha- and beta-spectrin subunits. Immunochemical analyses employing an affinity-purified polyclonal antibody to human erythrocyte beta-spectrin reacted specifically with the 220 kDa plant cell protein. Immunofluorescence microscopy indicated that the beta-spectrin antibody recognized an antigen which was primarily restricted to the peripheral areas of the cells. Collectively, these results suggest that the cells of higher plants contain polypeptides related to the spectrin family of proteins. It is proposed that the plant cell possesses a membrane skeleton which is structurally and perhaps functionally analogous to that of the animal cell.