Site-specific two-color protein labeling for FRET studies using split inteins.

Fluorescence resonance energy transfer (FRET) is an ideal tool for studying protein conformational changes and dynamics. Strategies to specifically label proteins with multiple colors at structurally important sites, a prerequisite for such studies, however, need to be devised on a protein-by-protein basis. Here we describe a simple yet widely applicable two-color site-specific protein labeling method utilizing Npu DnaE split intein.