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. SPTpT is the spore photoproduct of the TpT dinucleoside. Monomer or homodimer. Expressed at stage III of sporulation in the forespore compartment of the developing sporangium. Belongs to the radical SAM superfamily. SPL family.