IMMUNOLOGICAL ANALYSIS OF A SMALL GTP-BINDING PROTEIN IN HIGHER-PLANTCELLS

ara genes encoding YPT/RAB like small GTP-binding proteins, which are involved in the vesicular transport system in various eukaryotic cells , have been isolated from Arabidopsis thaliana. To determine the subce llular localization of ARA-4 protein, suspensions of cultured transgen ic tobacco cells were analyzed using monoclonal antibody to Arabidopsi s thaliana ARA-4 protein. ARA-4 protein was found in the microsomal me mbrane fraction. Similar results were obtained with Arabidopsis thalia na cells. The ARA-4 protein was readily released by detergents, such a s 0.5% sodium deoxycholate and NP-40. The results of immune-blot analy sis with extracts of different organs show that the ARA-4 protein is p resent in most organs of Arabidopsis thaliana plants, e. g. root, stem , flower and young fruit, at the same level in all organs except for r oot, where the level is lower.