We have reported that 130k-Da protein, newly isolated and cloned protein from rat brain in our laboratory, bound inositol 1,4,5-triphosphate and inositol 1,4,5,6-tetrakisphosphate with an equal affinity via its pleckstrin homology (PH) domain. In this study, we examined the specificity to various inositol polyphosphates or phosphoinositides using four types of recombinant PH domains derived from the N-terminal pleckstrin (PleNPH), RAC-protein kinase (RACPH), diacylglycerol kinase (DGKPH), and the 130k-Da protein (p!30PH). PleNPH, RACPH and DGKPH had the highest affinity to inositol 1.3,4,5,6-pentakisphosphate among inositol phosphates examined and the later two types also bound inositol 1,4,5,6tetrakisphosphate with a similar affinity, whereas pl30PH bound both inositol 1,4,5-trisphosphateand inositol 1,4,5,6-tetrakisphosphate. On the other hand, the PH domains of these molecules except for pleckstrin, showed a 10- to 40-times higher affinity to inositol 1,4,5-trisphosphate than that to corresponding phosphoinositide, phosphatidylinositol 4,5bisphosphate, while they had much the same affinity to inositol 1,3,4,5tetrakisphosphate and the corresponding phosphoinositide, phosphatidylinositol 3,4,5-trisphosphate. These data suggest that the most likely ligand for PH domain is inositol poiyphosphate/phosphoinositide. The determination of which phosphoinositide or its polar head is a physiologically relevant ligand would be dependent on the affinity and cellular abundance.
|出版ステータス||出版済み - 1997|
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