title: The carboxy-terminal αN helix of the archaeal XerA tyrosine recombinase is a molecular switch to control site-specific recombination.
abstract: Tyrosine recombinases are conserved in the three kingdoms of life. Here we present the first crystal structure of a full-length archaeal tyrosine recombinase, XerA from Pyrococcus abyssi, at 3.0 Å resolution. In the absence of DNA substrate XerA crystallizes as a dimer where each monomer displays a tertiary structure similar to that of DNA-bound Tyr-recombinases. Active sites are assembled in the absence of dif except for the catalytic Tyr, which is extruded and located equidistant from each active site within the dimer. Using XerA active site mutants we demonstrate that XerA follows the classical cis-cleavage reaction, suggesting rearrangements of the C-terminal domain upon DNA binding. Surprisingly, XerA C-terminal αN helices dock in cis in a groove that, in bacterial tyrosine recombinases, accommodates in trans αN helices of neighbour monomers in the Holliday junction intermediates. Deletion of the XerA C-terminal αN helix does not impair cleavage of suicide substrates but prevents recombination catalysis. We propose that the enzymatic cycle of XerA involves the switch of the αN helix from cis to trans packing, leading to (i) repositioning of the catalytic Tyr in the active site in cis and (ii) dimer stabilisation via αN contacts in trans between monomers.
authors.affiliation: Institut de Génétique et Microbiologie, Université Paris-Sud, Orsay, France. marie-claude.serre@igmors.u-psud.fr
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Serre
authors.forename: Toufic
authors.initials: T
authors.lastname: El Arnaout
authors.forename: Mark A
authors.initials: MA
authors.lastname: Brooks
authors.forename: Dominique
authors.initials: D
authors.lastname: Durand
authors.forename: Johnny
authors.initials: J
authors.lastname: Lisboa
authors.forename: Noureddine
authors.initials: N
authors.lastname: Lazar
authors.forename: Bertrand
authors.initials: B
authors.lastname: Raynal
authors.forename: Herman
authors.initials: H
authors.lastname: van Tilbeurgh
authors.forename: Sophie
authors.initials: S
authors.lastname: Quevillon-Cheruel
mesh_terms: D001051:Apoenzymes / Q000737:chemistry / Q000378:metabolism; D001483:Base Sequence; D018360:Crystallography, X-Ray; D019641:DNA, Archaeal / Q000235:genetics*; D008958:Models, Molecular; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D043903:Pyrococcus abyssi / Q000201:enzymology* / Q000235:genetics; D045522:Recombinases / Q000737:chemistry* / Q000378:metabolism*; D011995:Recombination, Genetic; D014443:Tyrosine
chemical_list: D001051:Apoenzymes; D019641:DNA, Archaeal; D045522:Recombinases; D014443:Tyrosine