Involved in repair of UV radiation-induced DNA damage during spore germination. Can repair thymine dimer 5-thyminyl-5,6-dihydrothymine (known as spore photoproduct (SP)) by in situ monomerization of SP to two thymines. (5R)-5,6-dihydro-5-(thymidin-7-yl)thymidine in DNA = a thymidine dimer in DNA Binds 1 [4Fe-4S] cluster per subunit. The cluster is coordinated with 3 cysteines and an exchangeable S-adenosyl-L-methionine. Binds 1 S-adenosyl-L-methionine per subunit. Monomer or homodimer. Belongs to the radical SAM superfamily. SPL family.