Cry1

Cry1, also known as cryptochrome-1, is a member of the cryptochrome family of flavoproteins. In plants and many microorganisms, Cry1 functions as a blue-light photoreceptor that helps regulate development and behavior in response to light. In vertebrates, Cry1 is part of the core molecular clock, working alongside Cry2 and other clock components to keep circadian rhythms aligned with the day-night cycle. Two cryptochrome genes, CRY1 and CRY2, encode these proteins in mammals; plants possess multiple cryptochrome genes that contribute to blue-light signaling.

Molecular features and mechanism

Cryptochromes have a photolyase-like domain and bind the cofactor flavin adenine dinucleotide (FAD). Although they are evolutionarily related to photolyases, cryptochromes generally lack DNA repair activity and instead serve signal transduction roles. In plants, blue light–activated Cry1 triggers a signaling cascade that influences gene expression and development, notably by interacting with other photoreceptors and transcription factors to promote photomorphogenesis. In animals, Cry1 acts primarily as a transcriptional repressor within the circadian feedback loop.

Role in circadian biology

In mammals, Cry1 contributes to the negative feedback portion of the circadian clock by repressing CLOCK-BMAL1–driven transcription of clock-controlled genes, including its own. This helps generate and stabilize ~24-hour rhythms that regulate sleep-wake cycles, metabolism, hormone release, and behavior. Cry1 functions are modulated by interactions with other clock proteins and post-translational modifications, and, in some species, by light input to peripheral clocks.

Significance

Cry1 is widely studied for its roles in light sensing, circadian biology, and seasonal and developmental processes. Its function contrasts across kingdoms, reflecting adaptation to diverse ecological niches and physiological needs.