Puertollano R, Menéndez M, Alonso M A
Centro de Biología Molecular "Severo Ochoa,", Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, Madrid, 28049-, Spain.
Biochem Biophys Res Commun. 1999 Dec 20;266(2):330-3. doi: 10.1006/bbrc.1999.1826.
The MAL proteolipid, an integral membrane protein with selective residence in glycolipid- and cholesterol-enriched membrane (GEM) microdomains, has recently been identified as being an element of the integral protein machinery necessary for apical transport in MDCK cells. With the use of a recombinant baculovirus, we have expressed and purified polyhistidine-tagged MAL to determine whether MAL has special lipid requirements for becoming incorporated into membranes. In contrast with caveolin-1, a component of GEMs that requires cholesterol for its integration into artificial membranes, MAL incorporation took place with dimyristoylphosphatidylcholine as the only lipid component. The presence of cholesterol, sphingomyelin, or galactocerebrosides did not affect the efficiency of this process. These results indicated that MAL is compatible with membranes containing either only phospholipids or also glycolipids and cholesterol and are consistent with the reported requirement of a sorting event for the specific targeting of MAL to GEM microdomains.
MAL蛋白脂质是一种整合膜蛋白，选择性存在于富含糖脂和胆固醇的膜（GEM）微结构域中，最近被确定为MDCK细胞顶端运输所需的完整蛋白质机制的一个组成部分。利用重组杆状病毒，我们表达并纯化了带有多组氨酸标签的MAL，以确定MAL整合到膜中是否有特殊的脂质需求。与小窝蛋白-1（GEM的一个成分，其整合到人工膜中需要胆固醇）不同，MAL的整合以二肉豆蔻酰磷脂酰胆碱作为唯一脂质成分时即可发生。胆固醇、鞘磷脂或半乳糖脑苷脂的存在并不影响这一过程的效率。这些结果表明，MAL与仅含磷脂或同时含糖脂和胆固醇的膜兼容，并且与报道的MAL特异性靶向GEM微结构域所需的分选事件要求一致。
