Suzuki K, Hirano H, Okutomi K, Suzuki M, Kuga Y, Fujiwara T, Kanemoto N, Isono K, Horie M
Second Department of Surgery, Chiba University School of Medicine, Japan.
DNA Res. 1997 Aug 31;4(4):273-80. doi: 10.1093/dnares/4.4.273.
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.
磷脂酰肌醇3激酶和4激酶催化结构域之间存在广泛的序列同源性，这使我们能够克隆出一个编码假定磷脂酰肌醇激酶NPIK的新人类基因。在其他已知的磷脂酰肌醇3激酶和4激酶中，NPIK与酵母PIK1磷脂酰肌醇4激酶关系最为密切。我们分离出了几种形式的NPIK cDNA，并在多种组织中检测到了NPIK信息的表达。荧光原位杂交和辐射杂种分析将NPIK基因定位于人类1号染色体。重组NPIK蛋白催化了磷脂酰肌醇向磷脂酰肌醇4磷酸的转化。NPIK的催化活性被曲拉通X-100增强，而在腺苷存在的情况下降低。利用绿色荧光蛋白系统，我们确定NPIK定位于细胞质中。综上所述，这些数据表明NPIK可能在从细胞质可及的位点调节磷脂酰肌醇4磷酸的合成中起关键作用。
