Sequencing and Preliminary Characterization of the Na+-Translocating NADH:Ubiquinone Oxidoreductase from Vibrio harveyi
详细信息 查看全文
- 作者：Weidong Zhou ; Yulia V. Bertsova ; Bintao Feng ; Panagiota Tsatsos ; Marina L. Verkhovskaya ; Robert B. Gennis ; Alexander V. Bogachev ; and Blanca Barquera
- 刊名：Biochemistry
- 出版年：1999
- 出版时间：December 7, 1999
- 年：1999
- 卷：38
- 期：49
- 页码：16246 - 16252
- 全文大小：253K
- 年卷期：v.38,no.49(December 7, 1999)
- ISSN：1520-4995
文摘
The Na+-translocating NADH: ubiquinone oxidoreductase (Na+-NQR) generates an electrochemical Na+ potential driven by aerobic respiration. Previous studies on the enzyme from Vibrioalginolyticus have shown that the Na+-NQR has six subunits, and it is known to contain FAD and an FeScenter as redox cofactors. In the current work, the enzyme from the marine bacterium Vibrio harveyi hasbeen purified and characterized. In addition to FAD, a second flavin, tentatively identified as FMN, wasdiscovered to be covalently attached to the NqrC subunit. The purified V. harveyi Na+-NQR wasreconstituted into proteoliposomes. The generation of a transmembrane electric potential by the enzymeupon NADH:Q1 oxidoreduction was strictly dependent on Na+, resistant to the protonophore CCCP, andsensitive to the sodium ionophore ETH-157, showing that the enzyme operates as a primary electrogenicsodium pump. Interior alkalinization of the inside-out proteoliposomes due to the operation of the Na+-NQR was accelerated by CCCP, inhibited by valinomycin, and completely arrested by ETH-157. Hence,the protons required for ubiquinol formation must be taken up from the outside of the liposomes, whichcorresponds to the bacterial cytoplasm. The Na+-NQR operon from this bacterium was sequenced, andthe sequence shows strong homology to the previously reported Na+-NQR operons from V. alginolyticusand Haemophilus influenzae. Homology studies show that a number of other bacteria, including a numberof pathogenic species, also have an Na+-NQR operon.