Kakinuma Y, Yamato I, Murata T
Faculty of Pharmaceutical Sciences, Chiba University, Japan.
J Bioenerg Biomembr. 1999 Feb;31(1):7-14. doi: 10.1023/a:1005499126939.
A Na+-translocating ATPase was discovered in a gram-positive bacterium Enterococcus hirae. Our biochemical and molecular biological studies revealed that this Na+-ATPase belongs to the vacuolar-type enzyme. Purified Na+-ATPase consisted of nine subunits: NtpA, B, C, D, E, F, G, I, and K; reconstituted proteoliposomes showed ATP-driven electrogenic Na+ translocation. All these subunits were encoded by the ntp operon: ntpFIKECGABDHJ. The deduced amino acid sequences of the major subunits, A, B, and K (16 kDa proteolipid), were highly similar to those of A, B, and proteolipid subunits of vacuolar ATPases, although the similarities of other subunits were moderate. The ntpJ gene encoded a K+ transporter independent of the Na+-ATPase. Expression of this operon, encoding two transport systems for Na+ and K+ ions, was regulated at transcriptional level by intracellular Na+ as the signal. Two related cation pumps, vacuolar Na+-ATPase and F0F1, H+-ATPase, coexist in this bacterium.
在革兰氏阳性菌海氏肠球菌中发现了一种钠转运ATP酶。我们的生物化学和分子生物学研究表明，这种钠ATP酶属于液泡型酶。纯化的钠ATP酶由九个亚基组成：NtpA、B、C、D、E、F、G、I和K；重组蛋白脂质体显示出ATP驱动的电致钠转运。所有这些亚基均由ntp操纵子编码：ntpFIKECGABDHJ。主要亚基A、B和K（16 kDa蛋白脂质）的推导氨基酸序列与液泡ATP酶的A、B和蛋白脂质亚基高度相似，尽管其他亚基的相似性中等。ntpJ基因编码一种独立于钠ATP酶的钾转运体。该操纵子编码钠和钾离子的两种转运系统，其表达在转录水平上受细胞内钠作为信号的调控。两种相关的阳离子泵，即液泡钠ATP酶和F0F1、H+-ATP酶，共存于这种细菌中。
