4.1.99.14 evolution enzyme SPL belongs to the radical SAM (S-adenosylmethionine) enzyme superfamily. The superfamily is defined by the characteristic tri-cysteinyl motif: CX3CX2C that binds to a [4Fe-4S] cluster -, 748849 4.1.99.14 evolution spore photoproduct lyase (SPL) is a member of the radical S-adenosyl-L-methionine (SAM) superfamily, the family members utilize S-adenosyl-Lmethionine (SAM) and a redox active [4Fe-4S] cluster to carry out diverse radical reactions including rearrangements, sulfur insertions and oxidations. Electron-nuclear double resonance and X-ray crystallography of several members of the superfamily have shown that the unique iron is coordinated by the amino and carboxylate moieties of S-adenosyl-L-methionine. An innersphere electron transfer from a reduced [4Fe-4S]+ cluster to the sulfonium of SAM leads to homolytic S-C(5') bond cleavage to generate a 5'-deoxyadenosyl radical (dAdo) intermediate, which abstracts a hydrogen atom from substrate to initiate a radical transformation -, 748241 4.1.99.14 evolution the enzyme is a member of the radical SAM superfamily -, 726998 4.1.99.14 evolution the enzyme is a member of the radical SAM superfamily, but SP lyase is the only known radical SAM enzyme to date catalyzing DNA repair. Clostridia SP lyases possess a conserved cysteine residue upstream the radical SAM motif (Cys74), which is substituted by a serine residue in Bacilli SP lyases -, 748852 4.1.99.14 evolution the enzyme is a member of the radical SAM superfamily, but SP lyase is the only known radical SAM enzyme to date catalyzing DNA repair. Clostridia SP lyases possess a conserved cysteine residue upstream the radical SAM motif (Cys74), which is substituted by a serine residue in Bacilli SP lyases. Cys74 in Ca SP lyase occupies a critical location similar to Cys140 in Gt SP lyase -, 748852 4.1.99.14 evolution the enzyme is a member of the radical SAM superfamily, but SP lyase is the only known radical SAM enzyme to date catalyzing DNA repair. Cys74 in Ca SP lyase occupies a critical location similar to Cys140 in Gt SP lyase -, 748852 4.1.99.14 evolution the enzyme is a member of the radical SAM superfamily, which is defined by the characteristic CXXXCXXC motif -, 748201 4.1.99.14 evolution the enzyme is a member of the so-called radical SAM superfamily, which is defined by the characteristic CXXXCXXC motif. The three cysteine residues serve as ligands respectively for three irons in the [4Fe-4S] cluster, with the fourth iron being coordinated by the S-adenosylmethionine in a bi-dentate manner, with its amino and carboxylate moieties serving as the fourth and fifth ligands to the cluster. SPL and the DNA photolyase, EC 4.1.99.3, show amino acid sequence homolgy and might have descended from a common ancestral protein -, 727074 4.1.99.14 evolution the enzyme is the first member of the radical SAM superfamily (comprising more than 44000 members) to bear a catalytically operating hydrogen atom transfer chain that is essential for S-adenosyl-L-methionine regeneration after the catalytic cycle -, 727020 4.1.99.14 evolution unlike DNA photolyases, EC 4.1.99.3, SP lyase belongs to the emerging superfamily of radical S-adenosyl-L-methionine (SAM) enzymes -, 728401 4.1.99.14 malfunction contrary to the C140A mutant, the double mutant repaires the DNA lesion without generating DNA adducts. Furthermore, in the crystal structure, the mutant S76C is shown to be at 4.1 A from the methylene bridge of SP which is a shorter distance than the one reported for the wild-type enzyme -, 748852 4.1.99.14 malfunction mutation at the remote glycine 168 residue alters the enzyme 3D structure, subsequently reducing the SPL activity by changing the positions of the essential amino acids involved in the radical transfer process -, 747837 4.1.99.14 malfunction the enzyme C141A mutant produces thymidylyl-(3'->5')-thymidylate likely via an unprecedented thymine radical cation reduction (proton coupled electron transfer) mechanism -, 726998 4.1.99.14 additional information a cysteine and two tyrosine residues are located in proximity and able to participate in the radical transfer process during the enzyme catalysis -, 747837 4.1.99.14 additional information active site structure of Gt SPL in complex with substrate and S-adenosyl-L-methionine, Cys140, Tyr96, and Tyr98 are active site residues, overview -, 748201 4.1.99.14 additional information active site structure, DNA lesion recognition, and substrate binding which involve a beta-hairpin structure, overview. S-adenosyl-L-methionine and a conserved cysteine residue are perfectly positioned in the active site for hydrogen atom abstraction from the dihydrothymine residue of the lesion and donation to the alpha-thyminyl radical moiety, respectively. Structure comparison of wild-type and C140 mutant enzymes, overview -, 728401 4.1.99.14 additional information combined Mössbauer, multi-edge X-ray absorption spectroscopic, and density functional theoretical study of theradical SAM enzyme spore photoproduct lyase, detailed overview. SPL requires S-adenosyl-L-methionine (SAM) and a redox active [4Fe-4S] cluster for catalysis -, 748241 4.1.99.14 additional information conformational changes associated with cofactor and substrate binding may serve to provide a solvent inaccessible and protected active site to safely catalyze radical reactions -, 747765 4.1.99.14 additional information Cys141, Tyr97, and Tyr99 are active site residues -, 748201 4.1.99.14 additional information residue C141 is solvent exposable and no other protein residue locates between the thymidylyl-(3'->5')-thymidylate radical and the C141 in the wild--type enzyme reaction pathway -, 726998 4.1.99.14 additional information residues Cys140 and Tyr98 are important for establishing catalytic turnover. While the allyl radical is situated and reduced at the 3'-side, transfer of the radical center back to the 5'-dAdoH requires moving the radical back to the 50-part in the active side over a distance of roughly 10 A. This creates next to a topological problem also an energetic obstacle, because regeneration of the adenosyl radical by the thiyl radical would be endothermic. The enzyme uses a further tyrosyl radical intermediate to solve the energetic and topological problem 727295 4.1.99.14 additional information spectral analysis of the purified recombinant enzyme, overview -, 715668 4.1.99.14 additional information the catalytic the cysteine residue is localized in a loop within the active site and in a very close proximity to the substrate at a distance of 4.5 A from the methylene bridge of the SP dimer -, 748852 4.1.99.14 additional information the enzyme protects at least 9 nucleotides in the spore photoproduct containing DNA strand with 5 nucleotides 3' to and 2 nucleotides 5' to the spore photoproduct damage, suggesting that the phosphates included in this region may be involved in the binding interaction with the enzyme -, 727074 4.1.99.14 additional information the repair of dinucleotide SP TpT by SPL(Ca) is 8-10-fold slower than that by SPL from Bacillus subtilis. The process also generates a large portion of the aborted product TpTSO2-. SPL(Ca) exhibits apparent (DV) kinetic isotope effects (KIEs) of about 6 and abnormally large competitive (DV/K) KIEs (about 20), both of which are much larger than the KIEs observed in from Bacillus subtilis. Clostridium acetobutilicum SPL(Ca) possesses a flexible active site and readily undergoes conformational changes during catalysis. Apparent (DV) kinetics isotope effect (KIE) determination, competitive (DV/K) KIE determination, and HDX-MS analysis of enzyme reaction and structure, overview -, 748849 4.1.99.14 physiological function on exposure of spores to UV radiation, an unique methylene bridged thymine dimer, 5-thyminyl-5,6-dihydrothymine (spore photoproduct or SP) accumulates as the main photoproduct. This accumulated photo-damage is rapidly repaired upon spore germination. Spore photoproduct lyase (SPL) catalyzes the repair of the UV lesion spore photoproduct (SP) in a reaction dependent on S-adenosyl-L-methionine (SAM) -, 747765 4.1.99.14 physiological function spore photoproduct lyase (SPL) catalyzes the direct reversal of a specific DNA photoproduct, 5-thyminyl-5,6-dihydrothymine (spore photoproduct or SP), back to two thymines. The methylene-bridged thymine dimer SP is the primary photoproduct when bacterial spores are subjected to UV radiation, and is rapidly repaired upon spore germination -, 748241 4.1.99.14 physiological function spore photoproduct lyase (SPL) catalyzes the direct reversal of a thymine dimer 5-thyminyl-5,6 dihydrothymine, i.e., the spore photoproduct (SP) to two thymine residues in germinating endospores -, 748849 4.1.99.14 physiological function spore photoproduct lyase (SPL) repairs 5-thyminyl-5,6-dihydrothymine, a thymine dimer that is also called the spore photoproduct (SP), in germinating endospores. SPL is a radical S-adenosylmethionine (SAM) enzyme, utilizing the 5'-deoxyadenosyl radical generated by SAM reductive cleavage reaction to revert SP to two thymine residues -, 748201 4.1.99.14 physiological function spore photoproduct lyase repairs a covalent UV-induced thymine dimer, spore photoproduct, in germinating endospores and is responsible for endospores' strong UV resistance. The spore photoproduct is rapidly repaired by the metalloenzyme spore photoproduct lyase when spores start germinating -, 726998 4.1.99.14 physiological function spore photoproduct lyase repairs a covalent UV-induced thymine dimer, spore photoproduct, in germinating endospores and is responsible for strong UV resistance of endospores -, 727020 4.1.99.14 physiological function spore photoproduct lyase repairs a special thymine dimer 5-thyminyl-5,6-dihydrothymine, which is commonly called spore photoproduct at the bacterial early germination phase. Spore photoproduct is the exclusive DNA photo-damage product in bacterial endospores. Its generation and swift repair by the enzyme are responsible for the spores' extremely high UV resistance -, 727074 4.1.99.14 physiological function the overwhelming majority of DNA photoproducts in UV-irradiated spores is a unique thymine dimer called spore photoproduct, SP, or 5-thymine-5,6-dihydrothymine. This lesion is repaired by the spore photoproduct lyase enzyme that directly reverts 5-thymine-5,6-dihydrothymine to two unmodified thymines. The SP lyase enzyme demonstrates an aspect of the diversity of DNA repair mechanisms in living organisms 680685 4.1.99.14 physiological function the radical SAM enzyme, spore photoproduct lyase, requires an H-atom transfer (HAT) pathway to catalyze DNA repair -, 747506 4.1.99.14 physiological function UV radiation triggers the formation of 5-thyminyl-5,6-dihydrothymine, i.e., the spore photoproduct (SP), in the genomic DNA of bacterial endospores. These SPs, if not repaired in time, may lead to genome instability and cell death. SP is mainly repaired by spore photoproduct lyase (SPL) during spore outgrowth via an unprecedented protein-harbored radical transfer pathway that is composed of at least a cysteine and two tyrosine residues. 5-thyminyl-5,6-dihydrothymine, i.e. the spore photoproduct (SP), is the dominant DNA photolesion found in bacterial endospores -, 747837