It is well known that camelids (camels and llamas) have fully functional antibodies with only a heavy chain consisting of a single variable domain and two constant domains. This single variable domain is called a "nanobody" and many nanobodies are synthesized in the cytosol of Escherichia coli, however, most of the nanobodies become inclusion bodies without tags to enhance their solubility. We generated a vector system to enable the secretary expression of nanobodies in Escherichia coli. In this system, several NBs were secreted into the culture supernatant. Since the vector contained 6xHis tag and AviTAG, biotinylation (even fluorescent-labeled) of AviTAG was achieved during cell culture, and purification of the supernatant was a step by immobilized metal ion adsorption chromatography. The procedure described in this study is believed to be as simple as regular plasmid minipreps. Therefore, many laboratories can use this method.

中文翻译：

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通过从大肠杆菌直接分泌可以简化纳米抗体的生产。

众所周知，骆驼科动物（骆驼和美洲驼）具有功能齐全的抗体，该抗体仅具有由单个可变结构域和两个恒定结构域组成的重链。该单个可变结构域被称为“纳米抗体”，并且许多纳米抗体在大肠杆菌的细胞质中合成，但是，大多数纳米抗体成为没有标签的包涵体，以增强其溶解性。我们生成了一个载体系统，可在大肠杆菌中表达纳米抗体。在该系统中，几个NB被分泌到培养上清液中。由于载体包含6xHis标签和AviTAG，因此在细胞培养过程中实现了AviTAG的生物素化（甚至荧光标记），上清液的纯化是通过固定化金属离子吸附色谱法进行的步骤。据信，这项研究中描述的程序与常规质粒微量制备方法一样简单。因此，许多实验室可以使用此方法。