Photolyase/Cryptochrom-Homologe aus Synechocystis sp. PCC 6803 und Arabidopsis thaliana: Funktion, Lokalisation und biochemische Eigenschaften

Table of Contents: Cryptochromes (CRY) are blue/UV-A photoreceptors related to the DNA-repair enzyme DNA-photolyase. So far, they have been found in plants, animals and humans. However, their evolutionary origin is unclear. Sequence comparisons indicated that cryptochromes may have arisen twice during evolution, the plant photoreceptors from the class I CPD DNA-photolyases, and the animal cryptochromes from (6-4) photolyases (Kobayashi et al., 2000). Here we show that the Synechocystis gene sll1629 encodes a cryptochrome type photoreceptor. Thus, cryptochromes already exist in cyanobacteria. Closely related to sll1629 is the Arabidopsis gene At5g24850. Its encoded protein carries a dual transit sequence and is targeted to chloroplasts and mitochondria. Thus, CRYs may have been transferred to plants from the photosynthetic endosymbiont. However, Arabidopsis CRY1 and CRY2 are only distantly related to sll1629 but more closely to sequences in ? -proteobacteria, which indicates that plants may have received the cryptochromes by a dual horizontal gene transfer.