title: Crystal structure of the left-handed archaeal RadA helical filament: identification of a functional motif for controlling quaternary structures and enzymatic functions of RecA family proteins.
abstract: The RecA family of proteins mediates homologous recombination, an evolutionarily conserved pathway that maintains genomic stability by protecting against DNA double strand breaks. RecA proteins are thought to facilitate DNA strand exchange reactions as closed-rings or as right-handed helical filaments. Here, we report the crystal structure of a left-handed Sulfolobus solfataricus RadA helical filament. Each protomer in this left-handed filament is linked to its neighbour via interactions of a beta-strand polymerization motif with the neighbouring ATPase domain. Immediately following the polymerization motif, we identified an evolutionarily conserved hinge region (a subunit rotation motif) in which a 360 degrees clockwise axial rotation accompanies stepwise structural transitions from a closed ring to the AMP-PNP right-handed filament, then to an overwound right-handed filament and finally to the left-handed filament. Additional structural and functional analyses of wild-type and mutant proteins confirmed that the subunit rotation motif is crucial for enzymatic functions of RecA family proteins. These observations support the hypothesis that RecA family protein filaments may function as rotary motors.
authors.affiliation: Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan.
authors.forename: Li-Tzu
authors.initials: LT
authors.lastname: Chen
authors.forename: Tzu-Ping
authors.initials: TP
authors.lastname: Ko
authors.forename: Yuan-Chih
authors.initials: YC
authors.lastname: Chang
authors.forename: Kuei-An
authors.initials: KA
authors.lastname: Lin
authors.forename: Chia-Seng
authors.initials: CS
authors.lastname: Chang
authors.forename: Andrew H-J
authors.initials: AH
authors.lastname: Wang
authors.forename: Ting-Fang
authors.initials: TF
authors.lastname: Wang
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017354:Point Mutation; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry; D051135:Rad51 Recombinase / Q000737:chemistry; D011938:Rec A Recombinases / Q000737:chemistry*; D012399:Rotation; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry; D016415:Sequence Alignment; D048229:Sulfolobus solfataricus / Q000201:enzymology
chemical_list: D019843:Archaeal Proteins; D004268:DNA-Binding Proteins; D021122:Protein Subunits; C117252:RadA protein, archaeal; D029701:Saccharomyces cerevisiae Proteins; D000255:Adenosine Triphosphate; D004247:DNA; C495151:RAD51 protein, S cerevisiae; D051135:Rad51 Recombinase; D011938:Rec A Recombinases