Inositol Polyphosphate Multikinase (IPMK)

IPMK, the deduced 416-amino acid protein has a calculated molecular mass of 47.2 kD. It contains an N-terminal inositol phosphate-binding site, a central ser-ser-leu-leu (SSLL) domain, a basic nuclear localization signal, and a C-terminal ATP-binding site. Fluorescence-tagged human IPMK localized predominantly in the nucleus of transfected rat kidney cells.Northern blot analysis detected ubiquitous expression of 6- and 4-kb IPMK transcripts, with highest levels in liver, followed by skeletal muscle, placenta, and peripheral blood leukocytes. This pattern of expression differed from that of rat Ipmk, which was highly expressed in kidney and brain.IPMK was unable to complement loss of its yeast homolog, Ipk2 (Arg82), suggesting that the human and yeast pathways differ.