DNA Repair: Photoreactivation


	UV light strikes one of the adjacent thymines, creating a thymine dimer.

		DNA photolyases recognize the “kink” in the DNA, and bind to the site.

		When excited by blue light (345-400 nm wavelength), the photolyases change conformation, breaking apart the dimer.

DNA photolyases, coded for by phr genes (photoreactivation), allow bacteria to repair the thymine dimers caused by UV exposure. Folate is used to “harvest” light energy, which is quickly transduced to FADH, making it FADH₂. The now-electronically excited FADH₂ can transfer the high-energy electron to the dimer, causing the structure to break apart into separate thymine molecules again.