Huang Kerwyn Casey, Mukhopadhyay Ranjan, Wingreen Ned S
Department of Molecular Biology, Princeton University, Princeton, New Jersey, United States of America.
PLoS Comput Biol. 2006 Nov 10;2(11):e151. doi: 10.1371/journal.pcbi.0020151. Epub 2006 Oct 4.
Subcellular protein localization is a universal feature of eukaryotic cells, and the ubiquity of protein localization in prokaryotic species is now acquiring greater appreciation. Though some targeting anchors are known, the origin of polar and division-site localization remains mysterious for a large fraction of bacterial proteins. Ultimately, the molecular components responsible for such symmetry breaking must employ a high degree of self-organization. Here we propose a novel physical mechanism, based on the two-dimensional curvature of the membrane, for spontaneous lipid targeting to the poles and division site of rod-shaped bacterial cells. If one of the membrane components has a large intrinsic curvature, the geometrical constraint of the plasma membrane by the more rigid bacterial cell wall naturally leads to lipid microphase separation. We find that the resulting clusters of high-curvature lipids are large enough to spontaneously and stably localize to the two cell poles. Recent evidence of localization of the phospholipid cardiolipin to the poles of bacterial cells suggests that polar targeting of some proteins may rely on the membrane's differential lipid content. More generally, aggregates of lipids, proteins, or lipid-protein complexes may localize in response to features of cell geometry incapable of localizing individual molecules.
亚细胞蛋白质定位是真核细胞的一个普遍特征，而蛋白质定位在原核生物中的普遍性如今正得到更多的认识。尽管已知一些靶向锚定物，但对于很大一部分细菌蛋白质来说，极性和分裂位点定位的起源仍然是个谜。最终，负责这种对称性破坏的分子成分必须具备高度的自组织能力。在此，我们基于膜的二维曲率提出了一种新颖的物理机制，用于脂质自发靶向杆状细菌细胞的两极和分裂位点。如果膜成分之一具有较大的固有曲率，那么更刚性的细菌细胞壁对质膜的几何约束自然会导致脂质微相分离。我们发现，由此产生的高曲率脂质簇足够大，能够自发且稳定地定位到细胞的两极。最近关于磷脂心磷脂定位到细菌细胞两极的证据表明，一些蛋白质的极性靶向可能依赖于膜的不同脂质组成。更普遍地说，脂质、蛋白质或脂质 - 蛋白质复合物的聚集体可能会根据细胞几何特征进行定位，而这些特征无法使单个分子定位。
