Structure and Function of Retinochrome

Retinochrome is a photo‐isomerase of all‐ trans ‐retinal to the 11‐ cis ‐isomer for rhodopsin synthesis. This protein is probably folded into seven α‐helices spanning the membranes. Upon irradiation, it is converted to metaretinochrome, via pre‐lumi‐ and lumiretinochrome, which are stable under 50 and 250 K, respectively. A series of analogue studies revealed that the cyclohexene ring and 6‐ s‐cis ‐twisted conformation are important for binding. Modification of the 14‐position suggests close location of the 14‐H to the counterion.