Immunocytochemical intracellular localization of the 22-ku Kunitz-type potato proteinase inhibitor in potato tubers and leaves

The twenty-two ku (kDa) Kunitz-type potato proteinase inhibitor (22-ku KPPI ) is synthesized as a preprotein with a hydrophobic signal sequence of 40 a mino acids. Using 22-ku KPPI specific antibody and GAR-IgG colloidal gold f or electron-microscopical immunocytochemistry, the 22-ku KPPI was localized mainly in the cell wall, with some detectable levels of label in or near p lasma membrane of cells in both tubers and non-wounded upper leaves from wo unded potatoes (Solanum tuberosum L). Neither vacuole nor the intercellular air space contained detectable levels of 22-ku KPPI.