All life on the earth uses a set of 20 amino acids to synthesize proteins according to the highly conservative codon table, and these limited kinds of amino acids serve as the building blocks for the natural protein synthesis. During the long-term evolution, nature is able to expand the structure and function of cellular proteins via changing the sequence order of amino acids. However, the evolution process is random and lack of controllability. Manipulating the structure and function of target proteins can also be realized by incorporating an expanded set of building blocks with new chemical and physical properties. Genetic code expansion for synthesis of proteins containing unnatural amino acids at any designed position can be achieved via the manipulation of the cellular components responsible for the translation step of the central dogma, which could endow target proteins with new and expanded properties. This review will be focused on the introduction of principles, strategies, techniques to engineer and rewire translational machinery and chassis underpinning genetic code expansion technology. Furthermore, emerging applications in the field of protein function regulation, innovative biomedicine and biocontainment relying on this technology will also be discussed.
Most lifes on the earth use a set of 20 naturally occurring amino acids as the building blocks for protein synthesis, according to the highly conserved codon table. Natural evolution modulates the structure and function of cellular proteins via random mutations among the limited, canonical collection of basic units. Instead, an expanded set of unnatural amino acids with new chemical and physical properties can be incorporated into proteins by synthetic biologists with molecular precision. Genetic code expansion for proteins can be achieved by engineering the translation step of the central dogma. This review will first introduce the principles, strategies, and techniques underpinning genetic code expansion technology, which targets the translational machinery in model chassis. Furthermore, related, emerging applications including protein function regulation, innovative biomedicine, and enhanced biocontainment will be discussed. We conclude with future perspectives.