title: Crosslinking and mass spectrometry suggest that the isolated NTD domain dimer of Moloney murine leukemia virus integrase adopts a parallel arrangement in solution.
abstract: BACKGROUND
  Retroviral integrases (INs) catalyze the integration of viral DNA in the chromosomal DNA of the infected cell. This reaction requires the multimerization of IN to coordinate a nucleophilic attack of the 3' ends of viral DNA at two staggered phosphodiester bonds on the recipient DNA. Several models indicate that a tetramer of IN would be required for two-end concerted integration. Complementation assays have shown that the N-terminal domain (NTD) of integrase is essential for concerted integration, contributing to the formation of a multimer through protein-protein interaction. The isolated NTD of Mo-MLV integrase behave as a dimer in solution however the structure of the dimer in solution is not known.
  
  
  RESULTS
  In this work, crosslinking and mass spectrometry were used to identify regions involved in the dimerization of the isolated Mo-MLV NTD. The distances between the crosslinked lysines within the monomer are in agreement with the structure of the NTD monomer found in 3NNQ. The intermolecular crosslinked peptides corresponding to Lys 20-Lys 31, Lys 24-Lys 24 and Lys 68-Lys 88 were identified. The 3D coordinates of 3NNQ were used to derive a theoretical structure of the NTD dimer with the suite 3D-Dock, based on shape and electrostatics complementarity, and filtered with the distance restraints determined in the crosslinking experiments.
  
  
  CONCLUSIONS
  The crosslinking results are consistent with the monomeric structure of NTD in 3NNQ, but for the dimer, in our model both polypeptides are oriented in parallel with each other and the contacting areas between the monomers would involve the interactions between helices 1 and helices 3 and 4.
authors.affiliation: Programa de Virologia ICBM, Facultad de Medicina, Universidad de Chile, Independencia 1027, Santiago, Chile.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Henriquez
authors.forename: Caifeng
authors.initials: C
authors.lastname: Zhao
authors.forename: Haiyan
authors.initials: H
authors.lastname: Zheng
authors.forename: José J
authors.initials: JJ
authors.lastname: Arbildua
authors.forename: Mónica L
authors.initials: ML
authors.lastname: Acevedo
authors.forename: Monica J
authors.initials: MJ
authors.lastname: Roth
authors.forename: Oscar
authors.initials: O
authors.lastname: Leon
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D019281:Dimerization; D019426:Integrases / Q000737:chemistry* / Q000378:metabolism; D013058:Mass Spectrometry; D051379:Mice; D062105:Molecular Docking Simulation; D008969:Molecular Sequence Data; D008979:Moloney murine leukemia virus / Q000201:enzymology*; D010455:Peptides / Q000032:analysis; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D055672:Static Electricity; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D010455:Peptides; D014764:Viral Proteins; D019426:Integrases