Properties of type II inositol polyphosphate 5-phosphatase.
We have isolated additional cDNA clones encoding type II inositol polyphosphate 5-phosphatase (5-phosphatase II) resulting in a combined cDNA of 3076 nucleotides encoding a protein of 942 amino acids. The 5-phosphatase II hydrolyzed both Ins(1,4,5)P3 to Ins(1,4)P2 and the phospholipid PtdIns(4,5)P2 to PtdIns(4)P both in vitro and in vivo. There are two motifs highly conserved between types I and II 5-phosphatase and several other proteins presumed to be inositol phosphatases suggesting a possible role in catalysis. The type II 5-phosphatase also contains homology to several GTPase activating proteins although no such activity for 5-phosphatase II was found. The predicted protein ends with the sequence CNPL, suggesting that it is isoprenylated as a mechanism for membrane attachment. We found evidence for isoprenylation by demonstrating incorporation of [3H]mevalonate into native but not C939S mutant 5-phosphatase II expressed in Sf9 insect cells. Furthermore, we showed that membrane localization and the activity of 5-phosphatase II toward its lipid substrate PtdIns(4,5)P2 is reduced by eliminating 5-phosphatase II isoprenylation in the mutant C939S relative to the native enzyme.
Jefferson
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Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Majerus
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PW
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D000072181:Inositol Polyphosphate 5-Phosphatases; D008969:Molecular Sequence Data; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017368:Protein Prenylation; D018411:Spodoptera
D010744:Phosphoric Monoester Hydrolases; D000072181:Inositol Polyphosphate 5-Phosphatases