The photolyase/cryptochrome family, a group of blue-light flavoproteins widely distributed throughout organisms, uses a highly conserved flavin adenine dinucleotide (FAD) cofactor to either repair UV-damaged DNA using blue-light (photolyase) or to act as a blue-light photoreceptor (cryptochrome). One member of the family, CRY-DASH, appears to be able to carry out both roles: DNA repair at high light intensity and blue-light signaling at low light intensity. The toggle between roles appears to be tied into the ability of the FAD cofactor to donate a proton from the FADH● state utilized in the DNA repair cycle. If the proton is donated, the result is the fully oxidized FAD state apparently needed in the blue-light photoreception cycle. We have found that there is an extreme pH dependence on the kinetics of the oxidation of FADH● to FAD and that the proton acceptor appears to have a pKA at 7.1. However, if UV-damaged DNA is bound the proton acceptor appears to become blocked, thereby stopping proton transfer and forcing CRY-DASH into the photolyase role in which FADH● would instead be reduced to FADH-. Stopped flow experiments have been initiated to measure the kinetics of oxidation of FADH- to FADH● in the presence and absence of UV-damaged DNA to test if the binding site of the FAD cofactor is altered upon substrate binding. This outcome could indicate that the proton acceptor is moved away from the FAD cofactor when UV-damaged DNA is present.

Cofactor oxidation state as a dictator of CRY-DASH function: Investigation into CRY-DASH FAD cofactor behavior in proximity to a proton accepting site

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.