Kaede (protein)

Kaede is a fluorescent protein that undergoes irreversible green-to-red photoconversion. It belongs to the class of coral-derived fluorescent proteins and is characterized by its unique ability to permanently shift its emission spectrum from green to red upon exposure to violet-to-blue light (typically around 488 nm or 405 nm).

The photoconversion process in Kaede involves cleavage of the peptide backbone at the chromophore, specifically between the Gly66 and Tyr67 residues. This cleavage results in an extension of the conjugated π-system within the chromophore, leading to the red-shifted emission. This photoconversion is irreversible, meaning that once the protein has switched to its red form, it cannot revert back to its green form.

Kaede is widely used as a tool in cell biology, developmental biology, and neuroscience for applications such as lineage tracing, protein tracking, and photoactivation. Its irreversible photoconversion makes it particularly useful for marking and following specific populations of cells or molecules over time, allowing researchers to study their movements and fates within complex biological systems. Because of its permanent conversion, it is useful for marking cells or organelles at one timepoint and then following them later.

Several variants of Kaede have been developed with improved brightness, photoconversion efficiency, or other desirable properties. These variants expand the utility of Kaede and its related photoconvertible fluorescent proteins in biological research. While Kaede was one of the first described proteins with this capability, many others have been developed since then.