Takase K, Kakinuma S, Yamato I, Konishi K, Igarashi K, Kakinuma Y
Department of Biological Science and Technology, Science University of Tokyo, Japan.
J Biol Chem. 1994 Apr 15;269(15):11037-44.
We have previously reported the DNA and amino acid sequences for the three genes (ntpA, ntpB, and ntpK) encoding the A, B, and K (proteolipid) subunits, respectively, of Na(+)-translocating ATPase of a eubacterium Enterococcus hirae (Kakinuma, Y., Kakinuma, S., Takase, K., Konishi, K., Igarashi, K., and Yamato, I. (1993) Biochem. Biophys. Res. Commun. 195, 1063-1069). In this paper we report the entire nucleotide sequence of the ntp gene cluster coding for this multisubunit enzyme. The cluster contained eight other genes; the order of these 11 genes was ntpF, -I, -K, -E, -C, -G, -A, -B, -D, -H, and -J, encoding proteins with predicted molecular weights of 14,255, 75,619, 16,036, 22,699, 38,162, 11,409, 65,766, 51,139, 27,093, 7,164, and 48,869, respectively. The deduced amino acid sequences of these products suggested that NtpI and NtpJ are hydrophobic proteins and others are hydrophilic. The ntpI gene product, which possesses six membrane-spanning segments in its carboxyl-terminal half, resembled the 116-kDa subunit of vacuolar (V)-ATPase in clathrin-coated vesicles. In addition, the NtpE, NtpC, NtpG, and NtpD proteins resembled bovine kidney ATPase E subunit, Saccharomyces cerevisiae Vma6p, Manduca sexta V-ATPase 14-kDa subunit, and Sulfolobus acidocaldarius gamma subunit, respectively, although the similarities between their amino acid sequences were moderate. Other gene products (NtpF and NtpH) did not show significant sequence similarity to other V-ATPase subunits. Since NtpA, NtpB, and NtpK are homologous counterparts of V-ATPase, these findings suggest that the molecular architecture of E. hirae Na(+)-ATPase complex corresponds to the V-type H(+)-ATPase complex distributed in various eukaryotic endomembrane systems. The sequence of the NtpJ product was similar to those of K+ transport systems of S. cerevisiae (Trk1 and Trk2); its meaning will be discussed. This is the first demonstration of a eukaryotic V-ATPase-like Na+ pump in bacteria.
我们之前已经报道了编码平肠球菌（Kakinuma, Y., Kakinuma, S., Takase, K., Konishi, K., Igarashi, K., and Yamato, I. (1993) Biochem. Biophys. Res. Commun. 195, 1063 - 1069）的Na⁺转运ATP酶的A、B和K（蛋白脂质）亚基的三个基因（ntpA、ntpB和ntpK）的DNA和氨基酸序列。在本文中，我们报道了编码这种多亚基酶的ntp基因簇的完整核苷酸序列。该基因簇还包含其他八个基因；这11个基因的顺序是ntpF、-I、-K、-E、-C、-G、-A、-B、-D、-H和-J，分别编码预测分子量为14,255、75,619、16,036、22,699、38,162、11,409、65,766、51,139、27,093、7,164和48,869的蛋白质。这些产物推导的氨基酸序列表明，NtpI和NtpJ是疏水蛋白，其他是亲水蛋白。NtpI基因产物在其羧基末端的一半具有六个跨膜区段，类似于网格蛋白包被小泡中液泡（V）-ATP酶的116 kDa亚基。此外，NtpE、NtpC、NtpG和NtpD蛋白分别类似于牛肾ATP酶E亚基、酿酒酵母Vma6p、烟草天蛾V-ATP酶14 kDa亚基和嗜酸热硫化叶菌γ亚基，尽管它们氨基酸序列之间的相似性一般。其他基因产物（NtpF和NtpH）与其他V-ATP酶亚基没有显著的序列相似性。由于NtpA、NtpB和NtpK是V-ATP酶的同源对应物，这些发现表明平肠球菌Na⁺-ATP酶复合物的分子结构与分布在各种真核内膜系统中的V型H⁺-ATP酶复合物相对应。NtpJ产物的序列与酿酒酵母（Trk1和Trk2）的K⁺转运系统的序列相似；其意义将进行讨论。这是首次在细菌中证明存在类似真核V-ATP酶的Na⁺泵。
