Location and mobility of ubiquinones of different chain lengths in artificial membrane vesicles.
Location and mobility of ubiquinones of different chain lengths in artificial membrane vesicles.
复制标题
不同链长的泛醌在人工膜囊泡中的位置和迁移率。
DOI：
10.1021/bi00331a016
复制
发表时间：
1985
期刊：
影响因子：
2.9
通讯作者：
Markley,JL
中科院分区：
文献类型：
--
作者：
Ulrich,EL;Girvin,ME;Cramer,WA;Markley,JL
美国普渡大学生物科学和化学系，西拉法叶，印第安纳州47907，1984年8月15日接收; 1984年11月28日修订的Mandarin pt接收摘要：将泛醌（UQ n，n = 2、3或10个类异戊二烯基团）掺入由二棕榈酰磷脂酰胆碱（DPPC）或二肉豆蔻酰磷脂酰胆碱（DMPC）制成的超声处理小泡中。(1)用紫外光谱法测定了DPPC和DMPC囊泡中氧化UQ对还原剂NaBH_4的可及性，其大小顺序为UQ_2> UQ_3> UQ_（10）（DPPC）和UQ_2> UQ_3 ~ UQ_（10）（DMPC）。(2)由外源性硼氢化钠还原包埋的铁氰化物的催化作用是更有效的与UQ 2比UQ 10，但慢于所有醌还原添加连二亚硫酸盐。(3)在DPPC和DMPC囊泡中，UQ 2和UQ 3的甲氧基质子表现出以~ 3.95 ppm为中心的单一NMR共振，而UQ 10的甲氧基基团在3.93 ppm处产生两个独立的质子共振，在3.78 ppm处产生更窄的共振。UQ 10人口的特点是由3.78 ppm的共振是目前在DPPC比DMPC囊泡浓度较高，是相对不敏感的NaBH 4减少。(4)UQ 10扰动DPPC囊泡的解链温度（Tm）的程度（Δ Tm =-1 ℃）小于UQ 2和UQ 3（Δ Tm =-3至-4 ℃）。组合的UV和NMR数据暗示以下：由3.78 ppm峰表征的UQ 10库对应于在2-3分钟内不被NaBH 4还原的更移动的UQm级分，并且被认为定位在接近DPPC双层的中心，因为它对DPPC Tm几乎没有影响。对应于3.93 ppm峰的DPPC囊泡中的UQ 10群体然后将对应于通过NaBH 4缓慢还原的UQ 10库，并且位于磁性上类似于UQ 2和UQ 3的双层环境中。UQ 2似乎位于双层表面附近，因为其对NaBH 4的可接近性和对脂质Tm的相对较大的影响。根据动力学数据，UQ 3的分布介于UQ 2和双层中心附近的UQ 10池之间，尽管UQ 3的磁环境似乎与UQ 2的磁环境相同。生理活性通常需要具有长类异戊二烯链的醌。目前的数据反对长链醌的跨膜“翻转”。有人提出，长链醌的一个基本属性的电子和质子转移的双分子层是它们的居住在疏水性的核心。
Departments of Biological Sciences andChemistry, Purdue University, West Lafayette, Indiana 47907 Received August 15, 1984; Revised Manuscript Received November 28, 1984 abstract: Ubiquinone (UQ „with «= 2, 3, or 10 isoprenoid groups) was incorporated into small, sonicated vesicles made of dipalmitoylphosphatidylcholine (DPPC) or dimyristoylphosphatidylcholine (DMPC).(1) The accessibility of oxidized UQ in DPPC or DMPC vesicles tothe reductant sodium borohydride (NaBH4), measured by UV spectroscopy, was UQ2> UQ3> UQ10 (DPPC) and UQ2> UQ3~ UQ10 (DMPC).(2) Catalysis of the reduction of entrapped ferricyanide by exogenous NaBH4 was more effective with UQ2 than UQ10 but was slower with all quiñones than reduction by added dithionite.(3) The methoxy protons of UQ2 and UQ3 in DPPC and DMPC vesicles exhibited a single NMR resonance centered at~ 3.95 ppm, whereas the methoxy groups of UQ10 gave riseto two separate proton resonances, at 3.93 ppm and a more narrow resonance at 3.78 ppm. The UQ10 population characterized by the 3.78 ppm resonance was present at a higher concentration in DPPC than in DMPC vesicles and was relatively insensitiveto reduction by NaBH4.(4) UQio perturbed the melting temperature (Tm) of DPPC vesicles to a smaller extent (ATm=-1 C) than did UQ2 and UQ3 (ATm=-3 to-4 C). The combined UV and NMR data imply the following: The UQio pool characterized by the 3.78 ppm peak corresponds to a more mobile UQm fraction that is not reduced by NaBH4 in 2-3 min and is thought to be localized close to the center of the DPPC bilayer since it has little effect on the DPPC Tm. The population of UQ10 in DPPC vesicles corresponding to the 3.93 ppm peak would then correspond to the UQi0 pool that is reduced slowly by NaBH4 and is located in a bilayer environment magnetically similar to that of UQ2 and UQ3. UQ2 appears to be positioned near the bilayer surface because of its accessibility to NaBH4 and relatively large effect on the lipid Tm. The distribution of UQ3 according to the kinetic data is intermediate between that of UQ2 and the UQio pool near the bilayer center, although the magnetic environment of UQ3 appears the same as that of UQ2. Physiological activities often require quiñones with long isoprenoid chains. The present data argue against transmembrane “flip-flop” of long-chain quiñones. It is proposed that one essential property of the long-chain quiñones for transfer of electrons and protons across the bilayer is their residence in the hydrophobic core.