Light‐Induced Conformational Changes in the Plant Cryptochrome Photolyase Homology Region Resolved by Selective Isotope Labeling and Infrared Spectroscopy

Conformational changes in the blue light receptor plant cryptochrome have been found in the C‐terminal extension (CCT), but few studies have addressed the changes in secondary structure in the sensory photolyase homology region (PHR). Here, we investigated the PHR by light‐induced infrared difference spectroscopy after establishing a global 13 C and 15 N labeling that preserves the chromophore flavin at natural abundance. As a result, difference bands are revealed that are assigned to prominent conformational changes in the PHR by illumination. We postulate that in addition to those in the CCT also changes in the PHR may mediate signaling events.