Relations between structure and function in cytoplasmic membrane vesicles isolated from an Escherichia coli fatty-acid auxotroph. High-angle x-ray diffraction, freeze-etch electron microscopy and transport studies.
Relations between structure and function in cytoplasmic membrane vesicles isolated from an Escherichia coli fatty-acid auxotroph. High-angle x-ray diffraction, freeze-etch electron microscopy and transport studies.
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从大肠杆菌脂肪酸营养缺陷型分离的细胞质膜囊泡的结构和功能之间的关系。
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发表时间：
1974
期刊：
影响因子：
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通讯作者：
T. Gulik
中科院分区：
文献类型：
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作者：
E. Shechter;L. Letellier;T. Gulik
本文提出的结果建立从大肠杆菌不饱和脂肪酸营养缺陷型分离的细胞质膜囊泡的结构，形态和功能特性之间的关系。从在油酸、亚油酸、亚麻酸或反油酸存在下生长的细胞中分离膜。
高角X-射线衍射研究表明，由温度变化引起的有序-无序转变与脂质的石蜡链是膜的脂肪酸组成的函数。在某些情况下，各种脂质物质的“共结晶”发生在单一类型的有序结构域内。在其他情况下，各种脂质物质分离成一种以上不同类型的有序结构域。
观察到的各种有序-无序转变诱导的疏水性核心的膜，这可以通过冷冻蚀刻电子显微镜检测到的形态变化。当脂质的石蜡链是无序的时，观察到颗粒在断裂面上的随机分布。在链烷烃链有序化时，颗粒被排除在有序区域之外，因此，观察到光滑区域和具有密集堆积颗粒的区域。光滑表面与颗粒化表面的比率与存在的有序链烷烃链的量成比例。此外，光滑域的大小是膜的脂肪酸组成的函数。
d-乳酸依赖的脯氨酸摄取率的不连续性作为温度的函数与观察到的有序-无序转变相关。在低温下的高活化能归因于聚集时载体蛋白的流动性降低。与此相反，磷酸烯醇化依赖的载体磷酸化不响应的石蜡链的排序。
The results presented in this paper establish relationships between structural, morphological and functional properties of cytoplasmic membrane vesicles isolated from an Escherichia coli unsaturated fatty acid auxotroph. The membranes were isolated from cells grown in the presence of either oleic, linoleic, linolenic or elaidic acids.
High-angle X-ray diffraction studies show that the order-disorder transitions induced by temperature variations and associated with the paraffin chains of the lipids are a function of the fatty acid composition of the membranes. In some cases “cocrystallization” of various lipid species takes place within a single type of ordered domains. In other cases there is segregation of various lipid species into more than one distinct type of ordered domain.
The various order-disorder transitions observed induce morphological changes in the hydrophobic core of the membranes which can be detected by freeze-etch electron microscopy. A random distribution of particles on the fracture faces is observed when the paraffin chains of the lipids are disordered. Upon ordering of the paraffin chains, particles are excluded from the ordered domains and as a consequence, smooth areas and areas with densely packed particles are observed. The ratio of the smooth surface to particulated surface is proportional to the amount of ordered paraffin chains present. Moreover, the size of the smooth domains is a function of the fatty acid composition of the membranes.
Discontinuities in the rate of d-lactate-dependent proline uptake as a function of temperature correlate with the order-disorder transitions observed. The high energies of activation at low temperatures are attributed to decreased mobility of the carrier proteins upon aggregation. In contrast, phosphoenolpyruvate-dependent vectorial phosphorylation does not respond to the ordering of the paraffin chains.