Adaptation mechanism of membrane lipids and its genetic control

从39℃到15℃，四膜虫细胞的温度变化引起膜磷脂脂肪酸组成的改变，饱和棕榈酸减少，不饱和脂肪酸如-亚油酸和亚油酸增加，通过ESR和冷冻断裂电镜可以推断其质膜更具流动性。低温驯化不影响细胞活力，但观察到单体聚集形成多聚体。多体含量的增加是否来源于新转录的mRNA尚不清楚。低温转移细胞中微粒体蛋白的二维凝胶电泳分析显示，微管蛋白和一些表观分子质量低于脂肪酰基辅酶a -去饱和酶的蛋白随时间增加。利用大鼠肝脏硬脂酰辅酶a去饱和酶cDNA的两个编码区，对四膜虫DNA进行Southern印迹。在35%甲酰胺和5xSSC的低强度条件下，28℃下24h， ecori酶切DNA与其中一个去饱和酶cDNA片段杂交。此外，EcoRV-和bglii -酶切的DNA分别显示2.6kb和2.7kb的杂交带，表明利用大鼠来源的DNA作为探针克隆四膜虫酶是可能的。

Temperature shift of Tetrahymena cells from 39 C to 15 C induced alterations in fatty acid composition of membrane phospholipids, a decrease in satureated palmitic acid and increases in unsaturated fatty acids such as -linoleinic and linoleic acids, causing its plasma membrane more fluid as inferred with ESR and freeze-fracture electron microscopy. Although low-temperature acclimation did not affect the viability of the cells, aggregation of monosome to form polysome was observed. Whether the increase in polysome content was derived from newly transcribed mRNA or not is to be clarified. Two dimensio- l gel electrophoretic analyses of microsomal proteins from low-temperature-shifted cells showed time-dependent increases in tubulin and some proteins which have lower apparent molecular masses than fatty acyl CoA-desaturase. Using two coding regions of rat liver stearyl-CoA desaturase cDNA, Southern blotting of Tetrahymena DNA was performed. Under low stringency of 35% formamide and 5xSSC, at 28 C for 24hr, EcoRI-digested DNA hybridized with one of the desaturase cDNA fragment. Furthermore, EcoRV- and BglII-digested DNA showed hybridizing bands of 2.6kb and 2.7kb, respectively, indicating a possibility of cloning Tetrahymena enzymes using rat-derived DNA as a probe.