Purification and characterization of receptors for myoinositol trisphosphate and myoinositol tetrakis phosphate from Entamoeba histolytica

The microsomal fraction from the log phase of Entamoeba histolytica cells contains Ins(1,4,5)P₃ and Ins(1,3,4,5)P₄ binding activity. The binding proteins/receptors for both Ins(1,4,5)P₃ and Ins(1,3,4,5)P₄ were purified and found to be specific for each ligand. The molecular masses for native proteins for InsP₃ and InsP₄ are 138 kDa and 130 kDa respectively having subunits of 69 kDa and 64 kDa respectively. That these proteins are associated with Ca²⁺ release was confirmed by including these proteins separately in proteoliposomes and adding InsP₃ and InsP₄ in both the cases.