A new inositol 1,4,5-trisphosphate binding protein similar to phospholipase C-delta 1.
We have reported that two inositol 1,4,5-trisphosphate binding proteins, with molecular masses of 85 and 130 kDa, were purified from rat brain; the former protein was found to be the delta 1-isoenzyme of phospholipase C (PLC-delta 1) and the latter was an unidentified novel protein [Kanematsu, Takeya, Watanabe, Ozaki, Yoshida, Koga, Iwanaga and Hirata (1992) J. Biol. Chem. 267, 6518-6525]. Here we describe the isolation of the full-length cDNA for the 130 kDa Ins(1,4,5)P3 binding protein, which encodes 1096 amino acids. The predicted sequence of the 130 kDa protein had 38.2% homology to that of PLC-delta 1. Three known domains of PLC-delta 1 (pleckstrin homology and putative catalytic X and Y domains) were located at residues 110-222, 377-544 and 585-804 with 35.2%, 48.2% and 45.8% homologies respectively. However, the protein showed no PLC activity to phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol. The 130 kDa protein expressed by transfection in COS-1 cells bound Ins(1,4,5)P3 in the same way as the molecule purified from brain. Thus the 130 kDa protein is a novel Ins(1,4,5)P3 binding protein homologous to PLC-delta 1, but with no catalytic activity. The functional significance of the 130 kDa protein is discussed.
Kanematsu
T
T
Department of Biochemistry, Faculty of Dentistry, Kyushu University, Fukuoka, Japan.
Misumi
Y
Y
Watanabe
Y
Y
Ozaki
S
S
Koga
T
T
Iwanaga
S
S
Ikehara
Y
Y
Hirata
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000201:enzymology; D015220:Calcium Channels / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007527:Isoenzymes / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D054803:Phospholipase C delta; D011485:Protein Binding; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics* / Q000378:metabolism*; D010738:Type C Phospholipases / Q000235:genetics* / Q000378:metabolism*
D015220:Calcium Channels; D018076:DNA, Complementary; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007527:Isoenzymes; D018160:Receptors, Cytoplasmic and Nuclear; D015544:Inositol 1,4,5-Trisphosphate; D010738:Type C Phospholipases; D054803:Phospholipase C delta; C518026:Plcd1 protein, rat