Rottem S, Markowitz O
J Bacteriol. 1979 Dec;140(3):944-8. doi: 10.1128/jb.140.3.944-948.1979.
Acholeplasma laidlawii cells grown with oleic acid produced much more colored carotenoids than did cells grown with elaidic acid. The amount of carotenoids was decreased 80 to 90% by growing the cells with 0.05 M propionate, resulting in a marked increase in the mobility of both 5-doxylstearate and 12-doxylstearate incorporated into the membranes. The fatty acid composition of the propionate-grown cells differed from that of cells grown without propionate by containing odd-numbered rather than even-numbered saturated fatty acids, but the ratios of saturated to unsaturated fatty acids were the same. To determine whether the carotenoids are the cause for the restricted mobility in the membranes, the carotenoids were selectively removed from A. laidlawii membranes by incubating the membranes with phosphatidylcholine vesicles. The carotenoid-depleted membranes showed an increase in the mobility of the hydrocarbon chains of the spin-labeled fatty acids. Furthermore, the incorporation of carotenoids into artificial membrane vesicles restricted the mobility of the hydrocarbon chain. Our results support the notion that the carotenoids in A. laidlawii act as a rigid insert reinforcing the membrane bilayer.
以油酸培养的莱氏无胆甾原体细胞比以反油酸培养的细胞产生的有色类胡萝卜素多得多。用0.05M丙酸盐培养细胞时，类胡萝卜素的量减少了80%至90%，这导致掺入膜中的5-羟基硬脂酸酯和12-羟基硬脂酸酯的流动性显著增加。丙酸盐培养的细胞的脂肪酸组成与未用丙酸盐培养的细胞不同，其含有奇数而非偶数的饱和脂肪酸，但饱和脂肪酸与不饱和脂肪酸的比例相同。为了确定类胡萝卜素是否是膜流动性受限的原因，通过将膜与磷脂酰胆碱囊泡孵育，从莱氏无胆甾原体膜中选择性去除类胡萝卜素。类胡萝卜素耗尽的膜显示自旋标记脂肪酸的烃链流动性增加。此外，将类胡萝卜素掺入人工膜囊泡会限制烃链的流动性。我们的结果支持这样的观点，即莱氏无胆甾原体中的类胡萝卜素作为一种刚性插入物增强了膜双层。
