Lepault J, Dargent B, Tichelaar W, Rosenbusch J P, Leonard K, Pattus F
European Molecular Biology Laboratory, Heidelberg, FRG.
EMBO J. 1988 Jan;7(1):261-8. doi: 10.1002/j.1460-2075.1988.tb02808.x.
Two dimensional crystals of maltoporin (or phage lambda receptor) were obtained by reconstitution of purified maltoporin trimers and Escherichia coli phospholipids by detergent dialysis. Two different trimer packing forms were observed. One was hexagonal (a = 7.8 nm) and one rectangular (a = 7.8 nm, b = 13.6 nm). In this paper we describe the three-dimensional structure of maltoporin, deduced from the study of the rectangular form by electron microscopy and image processing. At a resolution of approximately 2.5 nm, maltoporin trimers form aqueous channel triplets which appear to merge into a single outlet at the periplasmic surface of the outer membrane. The pore defined by maltoporin has a similar structure to that outlined by the matrix protein. From the results of functional studies by conductance measurement, it is concluded that the three channels defined by maltoporin act, contrary to those formed by the porin (OmpF protein), as a single conducting unit. A tentative outline of the maltoporin promoter is given. Maltoporin appears to be constituted by three different domains: a major rod-like domain spanning the membrane, a minor domain located near the periplasmic surface of the membrane and finally a central domain responsible for the splitting of the channel.
通过去污剂透析法将纯化的麦芽糖孔蛋白三聚体与大肠杆菌磷脂进行重构，获得了麦芽糖孔蛋白（或噬菌体λ受体）的二维晶体。观察到两种不同的三聚体堆积形式。一种是六边形（a = 7.8纳米），另一种是矩形（a = 7.8纳米，b = 13.6纳米）。在本文中，我们描述了麦芽糖孔蛋白的三维结构，该结构是通过电子显微镜和图像处理对矩形形式进行研究推导出来的。在大约2.5纳米的分辨率下，麦芽糖孔蛋白三聚体形成水性通道三联体，这些三联体似乎在外膜周质表面合并成一个单一的出口。麦芽糖孔蛋白所界定的孔与基质蛋白勾勒出的孔具有相似的结构。根据电导测量功能研究的结果，得出的结论是，与孔蛋白（OmpF蛋白）形成的通道相反，麦芽糖孔蛋白所界定的三个通道作为一个单一的传导单元起作用。给出了麦芽糖孔蛋白启动子的初步轮廓。麦芽糖孔蛋白似乎由三个不同的结构域组成：一个跨越膜的主要杆状结构域、一个位于膜周质表面附近的次要结构域以及最后一个负责通道分裂的中央结构域。
