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A radical transfer pathway in spore photoproduct lyase

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Benjdia,  Alhosna
Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Max Planck Society;

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Schlichting,  Ilme
Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Max Planck Society;

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Citation

Yang, L., Nelson, R. S., Benjdia, A., Lin, G., Telser, J., Stoll, S., et al. (2013). A radical transfer pathway in spore photoproduct lyase. Biochemistry, 52(18), 3041-3050. doi:10.1021/bi3016247.


Cite as: https://hdl.handle.net/11858/00-001M-0000-0019-8E91-9
Abstract
Spore 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 β 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.