Immunological Detection of an Inositol 1,4,5-Trisphosphate Receptor in Microsomes from Vicia faba (L.) and Zea mays (L.) and Broadbean Vacuoles

Membranes prepared from Vicia faba L. and Zea mays L. were analyzed by western immunoblot with an antibody raised against a mammalian inositoltrisphosphate (InsP3) receptor. In microsomes, from both plant species, the antibody cross-reacted with proteins of 260 and 252 kD, respectively. The isolated vacuoles from V. faba revealed the same pattern as microsomes, in contrast to plasma membranes purified by aqueous two-phase partitioning. Additionally, protein bands were found in the range of 45 kD in microsomes from Z. mays and 56 kD from V. faba microsomes and vacuoles (also in mouse microsomes). Thus, evidence is given for a plant InsP3 receptor associated with the tonoplast from V. faba with a corresponding molecular mass to the animal counterpart Microsomes from mouse brain as well as normal serum of rabbit were used for control.