Structural highlights
FunctionPublication Abstract from PubMedSpore photoproduct lyase (SPL) repairs a covalent UV-induced thymine dimer, spore photoproduct (SP), in germinating endospores and is responsible for the strong UV resistance of endospores. SPL is a radical S-adenosyl-l-methionine (SAM) enzyme, which uses a [4Fe-4S](+) cluster to reduce SAM, generating a catalytic 5'-deoxyadenosyl radical (5'-dA(*)). This in turn abstracts a H atom from SP, generating an SP radical that undergoes beta scission to form a repaired 5'-thymine and a 3'-thymine allylic radical. Recent biochemical and structural data suggest that a conserved cysteine donates a H atom to the thymine radical, resulting in a putative thiyl radical. Here we present structural and biochemical data that suggest that two conserved tyrosines are also critical in enzyme catalysis. One [Y99(Bs) in Bacillus subtilis SPL] is downstream of the cysteine, suggesting that SPL uses a novel hydrogen atom transfer (HAT) pathway with a pair of cysteine and tyrosine residues to regenerate SAM. The other tyrosine [Y97(Bs)] has a structural role to facilitate SAM binding; it may also contribute to the SAM regeneration process by interacting with the putative (*)Y99(Bs) and/or 5'-dA(*) intermediates to lower the energy barrier for the second H abstraction step. Our results indicate that SPL is the first member of the radical SAM superfamily (comprising more than 44000 members) to bear a catalytically operating HAT chain. A radical transfer pathway in spore photoproduct lyase.,Yang L, Nelson RS, Benjdia A, Lin G, Telser J, Stoll S, Schlichting I, Li L Biochemistry. 2013 May 7;52(18):3041-50. doi: 10.1021/bi3016247. Epub 2013 Apr, 22. PMID:23607538[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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