Ricchelli F, Gobbo S, Jori G, Salet C, Moreno G
C.N.R. Centre of Metalloproteins, Department of Biology, University of Padova, Italy.
Eur J Biochem. 1995 Oct 1;233(1):165-70. doi: 10.1111/j.1432-1033.1995.165_1.x.
The temperature dependence of hematoporphyrin and protoporphyrin fluorescence quantum yields (phi F) was studied after delivery to whole mitochondria or isolated inner (IMM) and outer (OMM) mitochondrial membranes, obtained from liver of Wistar rats. These studies are very sensitive to variations of the porphyrin lipid environment. Before incorporation, the porphyrins were dissolved in 0.01 M sodium phosphate, 0.15 M NaCl, pH 7.4) NaCl/Pi (only hematoporphyrin) or dispersed into liposomes of dipalmitoylphosphoglycerocholine (Pam2GroPCho), sometimes enriched with cholesterol or cardiolipin. Whole mitochondria show higher incorporation capacity of hematoporphyrin and protoporphyrin than isolated IMM and OMM, probably because additional, energy-sensitive transport mechanisms for the porphyrin uptake occur in intact organelles. A small decrease in protoporphyrin uptake is observed in OMM in comparison with IMM; in contrast, the decrease in hematoporphyrin uptake by OMM is rather significant. A comparison between the results obtained with IMM, OMM and whole mitochondria show that both porphyrins, when released to the intact organelles, preferentially localize in the IMM, irrespective of the lipid carrier used. NaCl/Pi-dissolved hematoporphyrin probably interacts with some membrane proteins, due to the similarity of the Arrhenius plots with those obtained for liposome-entrapped human serum albumin/hematoporphyrin complexes which were used as models to mimic hematoporphyrin-membrane protein binding sites. Liposomal hematoporphyrin and protoporphyrin bind to lipid domains. Hematoporphyrin accumulates in specific, localized lipid regions, perhaps in the boundary lipids area surrounding some inner-mitochondrial carriers; protoporphyrin accomodates in more rigid, lipid areas. On these bases, the higher photoactivity of hematoporphyrin, previously observed in mitochondria, in comparison with protoporphyrin, can be easily explained. Formation of linear dimers/aggregates, endowed with higher phi F than that of the monomers, are postulated to occur for both porphyrins only in the inner mitochondrial membrane.
研究了从Wistar大鼠肝脏获取的全线粒体或分离的线粒体内膜（IMM）和外膜（OMM）中，血卟啉和原卟啉荧光量子产率（phi F）的温度依赖性。这些研究对卟啉脂质环境的变化非常敏感。在掺入之前，卟啉溶解于0.01 M磷酸钠、0.15 M氯化钠、pH 7.4的NaCl/Pi（仅血卟啉）中，或分散于二棕榈酰磷脂酰甘油胆碱（Pam2GroPCho）脂质体中，有时还富含胆固醇或心磷脂。全线粒体显示出血卟啉和原卟啉的掺入能力高于分离的IMM和OMM，这可能是因为完整细胞器中存在额外的、对能量敏感的卟啉摄取转运机制。与IMM相比，OMM中原卟啉摄取量有小幅下降；相反，OMM中血卟啉摄取量的下降相当显著。对IMM、OMM和全线粒体所得结果的比较表明，两种卟啉释放到完整细胞器时，无论使用何种脂质载体，都优先定位于IMM。溶解于NaCl/Pi的血卟啉可能与某些膜蛋白相互作用，这是因为其阿累尼乌斯图与用作模拟血卟啉-膜蛋白结合位点模型的脂质体包裹的人血清白蛋白/血卟啉复合物所得的阿累尼乌斯图相似。脂质体血卟啉和原卟啉与脂质结构域结合。血卟啉积聚在特定的、局部的脂质区域，可能在一些线粒体内载体周围的边界脂质区域；原卟啉则容纳在更刚性的脂质区域。基于这些，先前在线粒体中观察到的血卟啉比原卟啉具有更高的光活性这一现象就很容易解释了。推测两种卟啉仅在线粒体内膜中形成具有比单体更高phi F的线性二聚体/聚集体。
