Liu Qun, Kriksunov Irina A, Wang Zhongwu, Graeff Richard, Lee Hon Cheung, Hao Quan
J Phys Chem B. 2008 Nov 27;112(47):14682-6. doi: 10.1021/jp807990g.
Proteins are macromolecules with characteristic structures and biological functions. It is extremely challenging to obtain protein microtube structures through self-assembly as proteins are very complex and flexible. Here we present a strategy showing how a specific protein, ADP-ribosyl cyclase, helically self-assembles from monomers into hexagonal nanochains and further to highly ordered crystalline microtubes. The structures of protein nanochains and consequently self-assembled superlattice were determined by X-ray crystallography at 4.5 A resolution and imaged by scanning electron microscopy. The protein initially forms into dimers that have a fixed size of 5.6 nm, and then, helically self-assembles into 35.6 nm long hexagonal nanochains. One such nanochain consists of six dimers (12 monomers) that stack in order by a pseudo P6(1) screw axis. Seven nanochains produce a series of large-scale assemblies, nanorods, forming the building blocks for microrods. A proposed aging process of microrods results in the formation of hollow microstructures. Synthesis and characterization of large scale self-assembled protein microtubes may pave a new pathway, capable of not only understanding the self-assembly dynamics of biological materials, but also directing design and fabrication of multifunctional nanobuilding blocks with particular applications in biomedical engineering.
蛋白质是具有特定结构和生物学功能的大分子。由于蛋白质非常复杂且具有柔韧性，通过自组装获得蛋白质微管结构极具挑战性。在此，我们展示了一种策略，即特定蛋白质——ADP核糖基环化酶如何从单体螺旋自组装成六边形纳米链，并进一步形成高度有序的晶体微管。通过X射线晶体学以4.5埃分辨率确定了蛋白质纳米链以及由此自组装的超晶格的结构，并通过扫描电子显微镜成像。该蛋白质最初形成大小固定为5.6纳米的二聚体，然后螺旋自组装成35.6纳米长的六边形纳米链。这样一条纳米链由六个二聚体（12个单体）组成，它们通过一个假P6(1)螺旋轴依次堆叠。七条纳米链产生一系列大规模组装体——纳米棒，形成微棒的构建单元。微棒的一个推测老化过程导致中空微结构的形成。大规模自组装蛋白质微管的合成与表征可能会开辟一条新途径，不仅能够理解生物材料的自组装动力学，还能指导多功能纳米构建单元的设计与制造，在生物医学工程中有特定应用。
