Soluble expression of enzymes inside the cell is a prerequisite for the successful biotransformation of valuable products. Some key enzymes involved in biotransformation processes, however, are hardly expressed in their soluble forms. Here, we propose an inducible plasmid display, which is a molecular evolution strategy coupled with a high-throughput screening and/or selection method, as a simple and powerful tool for improving the solubility of target enzymes. Specifically, the Oct-1 DNA-binding domain and intein (i.e., auto-processing domain) were employed as anchoring and protein trans-splicing motifs to develop the system, in which the probability of protein trans-splicing is dependent on the soluble property of target proteins. The applicability of inducible plasmid display was investigated using an α-1,2-fucosyltransferase (FucT2) from Helicobacter pylori, a highly insoluble and unstable enzyme in the cytoplasmic space of Escherichia coli, as a model protein. One round of the overall inducible plasmid display process, which consists of in vivo production of FucT2 mutants and in vitro screening, enabled soluble expression of FucT2 and selection of plasmids containing the corresponding genetic information. The inducible plasmid display developed in this study will contribute to the rapid and efficient screening and/or selection of soluble proteins.

细胞内酶的可溶性表达是有价值产品成功生物转化的先决条件。然而，一些参与生物转化过程的关键酶很难以其可溶形式表达。在这里，我们提出了一种诱导型质粒展示，这是一种分子进化策略，结合高通量筛选和/或选择方法，作为提高目标酶溶解度的简单而强大的工具。具体而言，OCT-1的DNA结合结构域和内含肽（即，自动处理域）被用作锚定和蛋白质反式剪接基序开发系统，其中蛋白质的概率反式剪接取决于靶蛋白的可溶性。使用来自幽门螺杆菌的 α-1,2-岩藻糖基转移酶 (FucT2)（一种在大肠杆菌细胞质空间中高度不溶且不稳定的酶）作为模型蛋白研究了诱导型质粒展示的适用性。一轮完整的诱导型质粒展示过程，包括FucT2 突变体的体内生产和体外筛选，使 FucT2 的可溶性表达和包含相应遗传信息的质粒的选择成为可能。本研究中开发的诱导型质粒展示将有助于快速有效地筛选和/或选择可溶性蛋白质。