In Vitro GT-array ( i -GT-ray), a Platform for Screening of Glycosyltransferase Activities and Protein-Protein Interactions

Progress in bioinformatics has facilitated the identification of a large number of putative glycosyltransferases (GTs) associated with many physiological processes. However, many of these GTs remain with unknown biochemical function due to numerous technical limitations. One of these limitations is the lack of innovative tools for large-scale screening of enzyme activity in vitro and testing protein-protein interactions (PPIs) between GT partners. Currently, testing the enzyme activity of a protein requires its production in a heterologous expression system and purification before enzyme assays, a process that is time-consuming and not amenable to high-throughput screening. To overcome this, we developed a platform called in vitro GT-array ( -GT-ray). In this platform, 96-well microplates are coated with plasmid DNA encoding for tagged GTs and a capture antibody. Tagged GTs are produced from plasmid DNA via a cell-free in vitro transcription/translation (IVTT) system and captured through the anti-tag capture antibody directly on microplates. After washing to remove IVTT components, the captured enzymes can be considered purified, and their activity can be tested directly on microplates. The whole process can be performed in less than two days, compared to several weeks for currently available screening methods. The -GT-ray platform has also been adapted to investigate PPIs between GTs. Here, we provide a practical user guide for the preparation of GT-arrays coated with plasmid DNA and a capture antibody that can be used for monitoring enzyme activity and PPIs of GTs in a high-throughput manner. Key features • Synthesis of tagged proteins directly from plasmid DNA, which are captured by anti-tag antibody attached to microplates. • Captured tagged proteins can be considered as purified proteins ready for enzyme assays. • Our platform can be used for high-throughput screening of enzyme activity and protein-protein interactions in vitro in a short time. • Our platform can be used for biochemical characterization of difficult proteins such as membrane-integrated glycosyltransferases. • Our platform can be adapted to downstream analytical methods such as mass spectrometry (i.e., DPS-MS).