PiUS (Pi uptake stimulator) is an inositol hexakisphosphate kinase.
A cDNA cloned from its ability to stimulate inorganic phosphate uptake in Xenopus oocytes (phosphate uptake stimulator (PiUS)) shows significant similarity with inositol 1,4,5-trisphosphate 3-kinase. However, the expressed PiUS protein showed no detectable activity against inositol 1,4,5-trisphosphate, nor the 1,3,4,5- or 3,4,5, 6-isomers of inositol tetrakisphosphate, whereas it was very active in converting inositol hexakisphosphate (InsP(6)) to inositol heptakisphosphate (InsP(7)). PiUS is a member of a family of enzymes found in many eukaryotes and we discuss the implications of this for the functions of InsP(7) and for the evolution of inositol phosphate kinases.
Schell
M J
MJ
Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, UK.
Letcher
A J
AJ
Brearley
C A
CA
Biber
J
J
Murer
H
H
Irvine
R F
RF
D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D019143:Evolution, Molecular; D006801:Humans; D007295:Inositol Phosphates; D008969:Molecular Sequence Data; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D017856:Phosphotransferases (Phosphate Group Acceptor) / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D010833:Phytic Acid / Q000378:metabolism; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014982:Xenopus laevis
D002352:Carrier Proteins; D018076:DNA, Complementary; D007295:Inositol Phosphates; D011993:Recombinant Fusion Proteins; C402123:inositol heptakisphosphate; D010833:Phytic Acid; D017856:Phosphotransferases (Phosphate Group Acceptor); C115134:IP6K1 protein, human; C099438:inositol hexakisphosphate kinase