Department of Medical Microbiology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, P.O. Box 30001, 9700 RB, Groningen, The Netherlands.
Appl Microbiol Biotechnol. 2017 Nov;101(22):8139-8149. doi: 10.1007/s00253-017-8524-x. Epub 2017 Oct 2.
The gram-positive bacterium Lactococcus lactis is a useful host for extracellular protein production. A main advantage of L. lactis over other bacterial expression systems is that lactococcal cells display low levels of autolysis and proteolysis. Previously, we developed a set of vectors for nisin-inducible extracellular production of N- or C-terminally hexa-histidine (His)-tagged proteins. The present study was aimed at expanding our portfolio of L. lactis expression vectors for protein purification and site-specific labeling. Specifically, we present two new groups of vectors allowing N- or C-terminal provision of proteins with a Strep-tag II or AVI-tag. Vectors for AVI-tagging encode an additional His-tag for protein purification. Another set of vectors allows removal of N-terminal Strep- or His-tags from expressed proteins with the tobacco etch virus protease. Two possible applications of the developed vectors are presented. First, we show that Strep-tagged LytM of Staphylococcus aureus in the growth medium of L. lactis can be directly bound to microtiter plates coated with an affinity reagent and used for enzyme-linked immunosorbent assays. Second, we show that the AVI-tagged Sle1 protein from S. aureus produced in L. lactis can be directly biotinylated and fluorescently labeled. The fluorescently labeled Sle1 was successfully applied for S. aureus re-binding studies, allowing subcellular localization by fluorescence microscopy. In conclusion, we have developed a set of expression vectors that enhances the versatility of L. lactis as a system for production of proteins with tags that can be used for affinity purification and site-specific protein labeling.
革兰氏阳性菌乳球菌(Lactococcus lactis)是一种用于胞外蛋白生产的有用宿主。与其他细菌表达系统相比,乳球菌的一个主要优势是细胞自溶和蛋白水解水平较低。先前,我们开发了一套用于乳链菌肽诱导的 N 端或 C 端六组氨酸(His)标记蛋白的胞外生产的载体。本研究旨在扩展我们用于蛋白纯化和定点标记的乳球菌表达载体组合。具体而言,我们提出了两组新的载体,允许在 N 端或 C 端提供带有 Strep-tag II 或 AVI-tag 的蛋白。用于 AVI 标记的载体为蛋白纯化编码了一个额外的 His 标签。另一组载体允许使用烟草蚀纹病毒蛋白酶从表达蛋白中去除 N 端的 Strep 或 His 标签。介绍了所开发载体的两种可能应用。首先,我们表明金黄色葡萄球菌的 LytM 在乳球菌的生长培养基中带有 Strep 标签,可以直接结合到用亲和试剂包被的微量滴定板上,并用于酶联免疫吸附测定。其次,我们表明金黄色葡萄球菌的 Sle1 蛋白在乳球菌中带有 AVI 标签,可以直接进行生物素化和荧光标记。荧光标记的 Sle1 成功地用于金黄色葡萄球菌再结合研究,通过荧光显微镜允许进行亚细胞定位。总之,我们开发了一组表达载体,增强了乳球菌作为生产带有可用于亲和纯化和定点蛋白标记标签的蛋白的系统的多功能性。