title: Solution structure and DNA binding of the catalytic domain of the large serine resolvase TnpX.
abstract: The transfer of antibiotic resistance between bacteria is mediated by mobile genetic elements such as plasmids and transposons. TnpX is a member of the large serine recombinase subgroup of site-specific recombinases and is responsible for the excision and insertion of mobile genetic elements that encode chloramphenicol resistance in the pathogens Clostridium perfringens and Clostridium difficile. TnpX consists of three structural domains: domain I contains the catalytic site, whereas domains II and III contain DNA-binding motifs. We have solved the solution structure of residues 1-120 of the catalytic domain I of TnpX. The TnpX catalytic domain shares the same overall fold as other serine recombinases; however, differences are evident in the identity of the proposed hydrogen donor and in the size, amino acid composition, conformation, and dynamics of the TnpX active site loops. To obtain the interaction surface of TnpX1-120 , we titrated a DNA oligonucleotide containing the circular intermediate joint attCI recombination site into (15) N-labeled TnpX1-120 and observed progressive nuclear magnetic resonance chemical shift perturbations using (15) N HSQC spectra. Perturbations were largely confined to a region surrounding the catalytic serine and encompassed residues of the active site loops. Utilizing the perturbation map and the data-driven docking program, HADDOCK, we have generated a model of the DNA interaction complex for the TnpX catalytic domain.
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, 3052, Australia.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Headey
authors.forename: Andrew
authors.initials: A
authors.lastname: Sivakumaran
authors.forename: Vicki
authors.initials: V
authors.lastname: Adams
authors.forename: Dena
authors.initials: D
authors.lastname: Lyras
authors.forename: Julian I
authors.initials: JI
authors.lastname: Rood
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Scanlon
authors.forename: Matthew C J
authors.initials: MC
authors.lastname: Wilce
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D020134:Catalytic Domain; D003016:Clostridium perfringens / Q000201:enzymology; D004269:DNA, Bacterial / Q000737:chemistry*; D062105:Molecular Docking Simulation; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D045522:Recombinases / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D045522:Recombinases; C497158:TnpX protein, Clostridium perfringens
keywords: NMR; TnpX; attCI; chloramphenicol resistance; serine recombinase; solution structure; transposon