Using synthetic small molecules to control biomolecules’ activity is a long term goal for scientists working at the chemistry and biology interface, and realizing highly specific modulation of biomolecules within living systems have draw particular attention in recent years. A research team led by Professor Peng Chen at the College of Chemistry and Molecular Engineering (CCME) at Peking University reported a chemical rescue strategy for restoring a specific protein’s function inside live cells, and their paper, entitled “Palladium-triggered deprotection chemistry for protein activation in living cells” was published online on Nature Chemistry website on March 16th.
Proteins are the workhorses of the cell, playing crucial roles in virtually every biological process. Employing small molecules or chemical reagents to modulate the function of an intracellular protein, particularly in a gain- of-function fashion, remains a challenge. In contrast to inhibitor-based loss-of-function approaches, methods based on a gain-of-function enable specific signalling pathways to be activated inside a cell. For example, a panel of small-molecule activators, the majority of which are allosteric activators, has been developed for switching on the intrinsic activity of enzymes and provides a way to ascertain the sufficiency of an enzyme in triggering a specific phenotype or cellular response. However, typically these small-molecule activators are identified by high-throughput screening or discovered by serendipity, and are thus not directly transferrable to other proteins.
Chen lab has a long interest in developing bioorthogonal chemical reactions in living cells. In this current work, they took advantages of the genetic expansion strategy as well as the palladium-mediated deprotection chemistry to creat a chemical rescue strategy that uses a palladium compound to activate a protein of interest within living cells. They first identified several biocompatible and efficient palladium catalysts that can cleave the propargyl-carbamate group from a protected lysine analogue, which permitted the in situ generation of a free lysine. This unnatural lysine analogue was then genetically and site-specifically incorporated into a protein, enabling the control over the reaction site. Such a deprotection strategy was subsequently shown to work with a range of different cell lines and proteins. Moreover, they further applied this biocompatible protection-group/catalyst pair for caging and release of a crucial lysine residue in a bacterial Type III effector protein within host cells, which revealed details of its virulence mechanism.
A Pd-mediated chemical decaging strategy for protein activation in living cells
This work offered a new approach for protein activation in living cells and added a new tool to the rapidly expanding repertoire of protein manipulation toolkits for living systems. Mr. Jie Li, a fourth year graduate student in CCME, is the first author of this paper. This work was supported by research grants from National Natural Science Foundation of China, the National Key Basic Research Foundation of China, Ministry of Education, Peking University, and Peking-Tsinghua Center for Life Sciences.