Jadot M, Dubois F, Wattiaux-De Coninck S, Wattiaux R
Laboratoire de Chimie Physiologique, Facultés Universitaires Notre-Dame de la Paix, Namur, Belgium.
Eur J Biochem. 1997 Nov 1;249(3):862-9. doi: 10.1111/j.1432-1033.1997.t01-1-00862.x.
Most lysosomal hydrolases are soluble enzymes. Lamp-II (lysosome-associated membrane protein-II) is a major constituent of the lysosomal membrane. We studied the aggregation of a series of lysosomal molecules. The aggregation-sensitive lysosomal marker enzymes were optimally aggregated at intralysosomal pH. A similar pH dependence was recorded for aggregation of Lamp-II. The pH-dependent loss of solubility of isolated Lamp-II required components of the lysosome extract. Conditions of mild acid pH promoting aggregation triggered the formation of complexes with lipids of lysosomal origin. We fractionated a membrane-free lysosome extract by gel-filtration chromatography and could reconstitute assemblies in vitro from separated fractions. We found some selectivity in the lysosomal proteins binding to complex lipids, phosphatidylcholine, sphingomyelin, and phosphatidylethanolamine being most effective. We propose that the formation at pH 5.0 of such supramolecular assemblies between lysosomal proteins and lipids occurs within the intralysosomal environment. Some possible consequences of such an intralysosomal matrix formation on organelle function are discussed.
大多数溶酶体水解酶都是可溶性酶。溶酶体相关膜蛋白II（Lamp-II）是溶酶体膜的主要成分。我们研究了一系列溶酶体分子的聚集情况。对聚集敏感的溶酶体标记酶在溶酶体内pH值条件下实现了最佳聚集。Lamp-II的聚集也呈现出类似的pH依赖性。分离出的Lamp-II在pH值依赖性条件下溶解度降低，这需要溶酶体提取物的成分参与。促进聚集的弱酸pH条件引发了与溶酶体来源脂质形成复合物。我们通过凝胶过滤色谱法对无膜溶酶体提取物进行了分级分离，并能够从分离出的组分在体外重新构建组装体。我们发现溶酶体蛋白与复合脂质结合存在一定的选择性，其中磷脂酰胆碱、鞘磷脂和磷脂酰乙醇胺最为有效。我们认为，在溶酶体内环境中，溶酶体蛋白与脂质之间在pH 5.0时会形成这种超分子组装体。本文还讨论了这种溶酶体内基质形成对细胞器功能可能产生的一些影响。
