Synthesis and application of caged peptides and proteins

Caged compounds have covalently attached groups that are rapidly cleaved upon exposure to UV light. Attachment of photolabile groups makes the molecule inert until photolysis releases it in its bioactive form. When caged compounds are applied to the experimental system in advance, the concentration jump of biologically active substances can be brought about immediately in a limited area upon irradiation with pulsed and focused UV light. Therefore, caged compounds of low molecular weight, which are commercially available, have been used effectively to study the mechanisms of temporal biological phenomena, such as muscle contraction, intracellular signaling, and neurotransmission. Because many proteins and peptides play important roles in these phenomena, their caged derivatives should serve as powerful tools to clarify complex biological systems. To prepare caged proteins and peptides, several groups have improved upon a chemical modification method, as well as developed two new methods: (1) nonsense codon suppression and (2) solid-phase peptide synthesis. In this review, we summarize recent advances made in the design, preparation, and application of caged peptides and proteins.