Pichler H, Gaigg B, Hrastnik C, Achleitner G, Kohlwein S D, Zellnig G, Perktold A, Daum G
Institut für Biochemie, Technische Universität, and SFB Biomembrane Research Center, Graz, Austria.
Eur J Biochem. 2001 Apr;268(8):2351-61. doi: 10.1046/j.1432-1327.2001.02116.x.
Large parts of the endoplasmic reticulum of the yeast, Saccharomyces cerevisiae, are located close to intracellular organelles, i.e. mitochondria and the plasma membrane, as shown by fluorescence and electron microscopy. Here we report the isolation and characterization of the subfraction of the endoplasmic reticulum that is closely associated with the plasma membrane. This plasma membrane associated membrane (PAM) is characterized by its high capacity to synthesize phosphatidylserine and phosphatidylinositol. As such, PAM is reminiscent of MAM, a mitochondria associated membrane fraction of the yeast [Gaigg, B., Simbeni, R., Hrastnik, C., Paltauf, F. & Daum, G. (1995) Biochim. Biophys. Acta 1234, 214-220], although the specific activity of phosphatidylserine synthase and phosphatidylinositol synthase in PAM exceeds several-fold the activity in MAM and also in the bulk endoplasmic reticulum. In addition, several enzymes involved in ergosterol biosynthesis, namely squalene synthase (Erg9p), squalene epoxidase (Erg1p) and steroldelta24-methyltransferase (Erg6p), are highly enriched in PAM. A possible role of PAM in the supply of lipids to the plasma membrane is discussed.
荧光显微镜和电子显微镜观察结果显示，酿酒酵母内质网的大部分区域靠近细胞内细胞器，即线粒体和质膜。在此，我们报告了与质膜紧密相关的内质网亚组分的分离和特性。这种与质膜相关的膜（PAM）的特征在于其合成磷脂酰丝氨酸和磷脂酰肌醇的能力很强。因此，PAM让人联想到MAM，即酵母中一种与线粒体相关的膜组分[Gaigg, B., Simbeni, R., Hrastnik, C., Paltauf, F. & Daum, G. (1995) Biochim. Biophys. Acta 1234, 214 - 220]，尽管PAM中磷脂酰丝氨酸合酶和磷脂酰肌醇合酶的比活性比MAM以及内质网总体中的活性高出数倍。此外，参与麦角固醇生物合成的几种酶，即鲨烯合酶（Erg9p）、鲨烯环氧酶（Erg1p）和甾醇δ24-甲基转移酶（Erg6p），在PAM中高度富集。本文还讨论了PAM在向质膜供应脂质方面可能发挥的作用。
