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Non-specific cysteine modifications on proteins induced by trans-cyclooctene
Zhijian Yan1,2, Wei Qin1,2,3,4,5,6
1School of Pharmaceutical Sciences, Tsinghua Medicine, Tsinghua University Beijing 100084 China weiqin@tsinghua.edu.cn.
None:
Tetrazine-trans-cyclooctene (Tz-TCO) click chemistry has been widely adopted for various applications due to its faster reaction kinetics and higher biocompatibility compared to conventional copper-catalyzed click chemistry. However, most click chemistry groups do not appear to be fully bioorthogonal, as several of them-including tetrazine-have been found to directly modify proteins. Here, we report the unexpected discovery of non-specific protein modifications by TCO during the development of a tetrazine-based proximity labeling method. TCO probes readily conjugate to cysteine residues on proteins, and pre-treatment with iodoacetamide significantly reduces TCO-mediated background labeling. Chemoproteomic analyses reveal that proteins involved in translation are heavily modified by TCO, pointing to potential off-target effects when TCO probes are used in live cells. Our findings underscore the need for further improving the biocompatibility of click chemistry to enable more precise biological applications.
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