title: Structural insights into recognition and repair of UV-DNA damage by Spore Photoproduct Lyase, a radical SAM enzyme.
abstract: Bacterial spores possess an enormous resistance to ultraviolet (UV) radiation. This is largely due to a unique DNA repair enzyme, Spore Photoproduct Lyase (SP lyase) that repairs a specific UV-induced DNA lesion, the spore photoproduct (SP), through an unprecedented radical-based mechanism. Unlike DNA photolyases, SP lyase belongs to the emerging superfamily of radical S-adenosyl-l-methionine (SAM) enzymes and uses a [4Fe-4S](1+) cluster and SAM to initiate the repair reaction. We report here the first crystal structure of this enigmatic enzyme in complex with its [4Fe-4S] cluster and its SAM cofactor, in the absence and presence of a DNA lesion, the dinucleoside SP. The high resolution structures provide fundamental insights into the active site, the DNA lesion recognition and binding which involve a β-hairpin structure. We show that SAM 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 α-thyminyl radical moiety, respectively. Based on structural and biochemical characterizations of mutant proteins, we substantiate the role of this cysteine in the enzymatic mechanism. Our structure reveals how SP lyase combines specific features of radical SAM and DNA repair enzymes to enable a complex radical-based repair reaction to take place.
authors: Department of Biomolecular Mechanisms, Max-Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany. Alhosna.Benjdia@mpimf-heidelberg.mpg.de
authors: Alhosna
authors: A
authors: Benjdia
authors: Korbinian
authors: K
authors: Heil
authors: Thomas R M
authors: TR
authors: Barends
authors: Thomas
authors: T
authors: Carell
authors: Ilme
authors: I
authors: Schlichting
mesh_terms: D001665:Binding Sites; D020134:Catalytic Domain; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D056506:Geobacillus / Q000201:enzymology; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D011506:Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D011506:Proteins; D012436:S-Adenosylmethionine; D004247:DNA; C088014:spore photoproduct lyase; D045643:DNA Repair Enzymes