Adaptation mechanism of membrane lipids and its genetic control

温度变化的四膜虫细胞从39 C至15 C诱导膜磷脂的脂肪酸组成的改变，饱和棕榈酸的减少和不饱和脂肪酸，如-亚油酸和亚油酸的增加，导致其质膜更多的流体推断与ESR和冷冻断裂电子显微镜。虽然低温驯化不影响细胞的活力，但观察到单体聚集形成多聚体。多核糖体含量的增加是否来源于新转录的mRNA还有待澄清。对低温细胞微粒体蛋白质的二维凝胶电泳分析表明，微管蛋白和某些表观分子量低于脂酰辅酶A去饱和酶的蛋白质随时间增加。利用大鼠肝硬脂酰辅酶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的低严谨度下，在28 ℃下24小时，EcoRI消化的DNA与其中一个去饱和酶cDNA片段杂交。此外，EcoRV和BglII消化的DNA分别显示2.6kb和2.7kb的杂交带，表明使用大鼠来源的DNA作为探针克隆四膜虫酶的可能性。

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.