Identification and characterization of a novel human phosphatidylinositol 4-kinase.
The extensive sequence homology that exists among the catalytic domains of phosphatidylinositol 3- and 4-kinases allowed us to clone a novel human gene encoding a putative phosphatidylinositol kinase, NPIK. Among other known phosphatidylinositol 3- and 4-kinases, NPIK was most closely related to yeast PIK1 phosphatidylinositol 4-kinase. Several forms of NPIK cDNAs were isolated, and expression of NPIK message was detected in a wide variety of tissues. Fluorescence in situ hybridization and radiation hybrid analyses assigned the NPIK gene to human chromosome 1. Recombinant NPIK protein catalyzed a conversion from phosphatidylinositol to phosphatidylinositol 4-phosphate. The catalytic activity of NPIK was augmented by Triton X-100, and was reduced in the presence of adenosine. Using green fluorescent protein system we determined that NPIK is localized in the cytoplasm. Taken together, the data suggest that NPIK may play a pivotal role in regulating the synthesis of phosphatidylinositol 4-phosphate at the site(s) accessible from cytoplasm.
Suzuki
K
K
Second Department of Surgery, Chiba University School of Medicine, Japan.
Hirano
H
H
Okutomi
K
K
Suzuki
M
M
Kuga
Y
Y
Fujiwara
T
T
Kanemoto
N
N
Isono
K
K
Horie
M
M
D019870:1-Phosphatidylinositol 4-Kinase / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D002878:Chromosomes, Human, Pair 1; D003001:Cloning, Molecular; D018076:DNA, Complementary; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D013347:Subcellular Fractions / Q000201:enzymology
D018076:DNA, Complementary; D012333:RNA, Messenger; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D019870:1-Phosphatidylinositol 4-Kinase; C441760:PIK1 protein, S cerevisiae