BIOCHEMICAL AND IMMUNOCYTOCHEMICAL CHARACTERIZATION OF MONOCLONAL-ANTIBODY TOP-35 RAISED AGAINST PURIFIED TONOPLAST FROM CRESS ROOT

The vacuolar membrane, the tonoplast, is a protein-rich membrane hithe rto only few proteins in it have been identified, As an approach for t he identification of tonoplast proteins by monoclonal antibodies (MABs ), purified tonoplast from cress roots (Lepidium sativum L.) were used for immunization and plasma membranes as a control membrane to test t he absence of antigen, The MAB TOP 35 identified a glycoprotein of abo ut 35 kDa in purified tonoplast of cress roots, Triton X-114 phase sep aration showed that it was a hydrophobic integral membrane protein, In immunocytochemistry the MAB TOP 35 strongly labelled the vacuolar mem brane. The absence of cell wall or plasma membrane labelling by TOP 35 indicates a distinct biosynthetic pathway of this protein to the vacu olar membrane in plants.