McElhaney R N
Department of Biochemistry, University of Alberta, Edmonton, Canada.
Subcell Biochem. 1993;20:53-108. doi: 10.1007/978-1-4615-2924-8_3.
It should be clear from this summary that we currently know a great deal about the organization and dynamics of the lipids in mycoplasma membranes in general, and in the cell membrane of A. laidlawii in particular. In fact, research on mycoplasma membranes has been important in unambiguously establishing the fundamental lipid bilayer structure of all biological membranes and in elucidating some of the major properties of bilayers in biomembranes, such as their thermotropic phase behavior and interactions with cholesterol and membrane proteins. Although a great deal has been learned, a number of issues have not been fully resolved. In particular, the concept of membrane lipid fluidity must be refined and quantitated, and the relationship between orientational order and rates of motion better understood. This will require that the apparent discrepancies between some of the results obtained, for example, by the various spectroscopic techniques, be resolved. In particular, the nature of the boundary lipid surrounding integral membrane proteins will require further study, as will the question of the specificity of lipid-protein interactions. Also, accurate quantitative measurements for the lateral and rotational mobilities of the various lipid components in the mycoplasma membranes have not yet been made. Although not reviewed in this chapter, the related questions of the in vivo rate of phospholipid, glycolipid, and cholesterol transverse diffusion (flip-flop), and the possible asymmetric transbilayer distribution of these components in mycoplasma membranes, are still not well understood. Although much remains to be done, particularly with respect to our understanding of protein structure and function in mycoplasma membranes, a solid basis for further advances has now been laid. The many natural advantages of mycoplasma for biochemical and biophysical investigations of membrane structure and function should continue to make these organisms very useful for membrane studies for years to come.
从这个总结中应该可以清楚地看到，我们目前对支原体膜中的脂质组织和动态，特别是莱氏无胆甾原体细胞膜中的脂质组织和动态，有了很多了解。事实上，对支原体膜的研究对于明确确立所有生物膜的基本脂质双层结构，以及阐明生物膜中双层的一些主要特性，如它们的热致相行为以及与胆固醇和膜蛋白的相互作用，具有重要意义。尽管已经了解了很多，但仍有一些问题尚未完全解决。特别是，膜脂质流动性的概念必须加以完善和量化，并且取向有序性与运动速率之间的关系需要更好地理解。这将要求解决例如通过各种光谱技术获得的一些结果之间明显的差异。特别是，围绕整合膜蛋白的边界脂质的性质需要进一步研究，脂质 - 蛋白相互作用的特异性问题也需要进一步研究。此外，尚未对支原体膜中各种脂质成分的横向和旋转流动性进行准确的定量测量。尽管本章未对此进行综述，但磷脂、糖脂和胆固醇横向扩散（翻转）的体内速率以及这些成分在支原体膜中可能的不对称跨双层分布等相关问题，仍未得到很好的理解。尽管还有很多工作要做，特别是在我们对支原体膜中蛋白质结构和功能的理解方面，但现在已经奠定了进一步进展的坚实基础。支原体在膜结构和功能的生化及生物物理研究方面具有许多天然优势，在未来几年，这些生物体对于膜研究仍将非常有用。
