HIGH-AFFINITY INOSITOL 1,3,4,5-TETRAKISPHOSPHATE RECEPTOR FROM RAT-LIVER NUCLEI - PURIFICATION, CHARACTERIZATION, AND AMINO-TERMINAL SEQUENCE

Inositol 1,3,4,5-tetrakisphosphate (InsP(4)) mediates nuclear calcium signaling [Koppler P., Matter, N., & Malviya A. N. (1993) J. Biol. Che m. 268, 26248-26252], and a distinct high affinity InsP(4) binding sit e is identified with rat liver nuclei [Koppler, P., Mersel, M., & Malv iya, A. N. (1994) Biochemistry 33, 14707-14713] as compared with other rat liver membrane fractions. A novel InsP(4) receptor protein derive d from rat liver nuclei has been purified to apparent homogeneity empl oying preparative isoelectric focusing, electrophoretic mobility, nond enaturating polyacrylamide gel electrophoresis, and electroelution. Is oelectric focusing indicated an isoelectric pH around 4.3 +/- 0.2 whic h was further confirmed by bidimensional electrophoresis. The high aff inity nuclear InsP(4) receptor was identified as a 74 kDa protein both on the SDS-PAGE and on the bidimensional electrophoresis. Partial mic rosequence analysis showed that the N-terminal end of nuclear InsP(4) receptor consists of amino acids: PNHKNEIAGNFS.. The 74 kDa nuclear In sP(4) receptor protein is a distinct protein from the other InsP(4) re ceptors purified from other sources and documented in the literature.