title: Structures of TraI in solution.
abstract: Bacterial conjugation, a DNA transfer mechanism involving transport of one plasmid strand from donor to recipient, is driven by plasmid-encoded proteins. The F TraI protein nicks one F plasmid strand, separates cut and uncut strands, and pilots the cut strand through a secretion pore into the recipient. TraI is a modular protein with identifiable nickase, ssDNA-binding, helicase and protein-protein interaction domains. While domain structures corresponding to roughly 1/3 of TraI have been determined, there has been no comprehensive structural study of the entire TraI molecule, nor an examination of structural changes to TraI upon binding DNA. Here, we combine solution studies using small-angle scattering and circular dichroism spectroscopy with molecular Monte Carlo and molecular dynamics simulations to assess solution behavior of individual and groups of domains. Despite having several long (>100 residues) apparently disordered or highly dynamic regions, TraI folds into a compact molecule. Based on the biophysical characterization, we have generated models of intact TraI. These data and the resulting models have provided clues to the regulation of TraI function.
authors.affiliation: NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Mail Stop 6102, Gaithersburg, MD, 20899, USA.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Clark
authors.forename: Madushi
authors.initials: M
authors.lastname: Raththagala
authors.forename: Nathan T
authors.initials: NT
authors.lastname: Wright
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Buenger
authors.forename: Joel F
authors.initials: JF
authors.lastname: Schildbach
authors.forename: Susan
authors.initials: S
authors.lastname: Krueger
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Curtis
mesh_terms: D002942:Circular Dichroism; D003227:Conjugation, Genetic; D004265:DNA Helicases / Q000737:chemistry* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D009010:Monte Carlo Method; D033363:Neutron Diffraction; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D053838:Scattering, Small Angle; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction
chemical_list: D029968:Escherichia coli Proteins; C027093:TraI protein, E coli; D004265:DNA Helicases