title: Protein structure. Direct observation of structure-function relationship in a nucleic acid-processing enzyme.
abstract: The relationship between protein three-dimensional structure and function is essential for mechanism determination. Unfortunately, most techniques do not provide a direct measurement of this relationship. Structural data are typically limited to static pictures, and function must be inferred. Conversely, functional assays usually provide little information on structural conformation. We developed a single-molecule technique combining optical tweezers and fluorescence microscopy that allows for both measurements simultaneously. Here we present measurements of UvrD, a DNA repair helicase, that directly and unambiguously reveal the connection between its structure and function. Our data reveal that UvrD exhibits two distinct types of unwinding activity regulated by its stoichiometry. Furthermore, two UvrD conformational states, termed "closed" and "open," correlate with movement toward or away from the DNA fork.
authors.affiliation: Department of Physics, Center for the Physics of Living Cells, and Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Comstock
authors.affiliation: Department of Physics, Center for the Physics of Living Cells, and Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Whitley
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA.
authors.forename: Haifeng
authors.initials: H
authors.lastname: Jia
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA.
authors.forename: Joshua
authors.initials: J
authors.lastname: Sokoloski
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA.
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Lohman
authors.affiliation: Department of Physics, Center for the Physics of Living Cells, and Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. Howard Hughes Medical Institute, Urbana, IL 61801, USA. Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Taekjip
authors.initials: T
authors.lastname: Ha
authors.affiliation: Department of Physics, Center for the Physics of Living Cells, and Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. ychemla@illinois.edu.
authors.forename: Yann R
authors.initials: YR
authors.lastname: Chemla
mesh_terms: D004265:DNA Helicases / Q000737:chemistry* / Q000502:physiology*; D004260:DNA Repair; D004261:DNA Replication; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000502:physiology*; D008856:Microscopy, Fluorescence / Q000379:methods; D052898:Optical Tweezers; D011487:Protein Conformation; D013329:Structure-Activity Relationship
chemical_list: D029968:Escherichia coli Proteins; C506746:UvrD protein, E coli; D004265:DNA Helicases