title: Crystal structure of E. coli RecE protein reveals a toroidal tetramer for processing double-stranded DNA breaks.
abstract: Escherichia coli RecE protein is part of the classical RecET recombination system that has recently been used in powerful new methods for genetic engineering. RecE binds to free double-stranded DNA (dsDNA) ends and processively digests the 5'-ended strand to form 5'-mononucleotides and a 3'-overhang that is a substrate for single strand annealing promoted by RecT. Here, we report the crystal structure of the C-terminal nuclease domain of RecE at 2.8 A resolution. RecE forms a toroidal tetramer with a central tapered channel that is wide enough to bind dsDNA at one end, but is partially plugged at the other end by the C-terminal segment of the protein. Four narrow tunnels, one within each subunit of the tetramer, lead from the central channel to the four active sites, which lie about 15 A from the channel. The structure, combined with mutational studies, suggests a mechanism in which dsDNA enters through the open end of the central channel, the 5'-ended strand passes through a tunnel to access one of the four active sites, and the 3'-ended strand passes through the plugged end of the channel at the back of the tetramer.
authors.affiliation: Department of Molecular and Cellular Biochemistry, The Ohio State University College of Medicine, Columbus, OH 43210, USA.
authors.forename: Jinjin
authors.initials: J
authors.lastname: Zhang
authors.forename: Xu
authors.initials: X
authors.lastname: Xing
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Herr
authors.forename: Charles E
authors.initials: CE
authors.lastname: Bell
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D005090:Exodeoxyribonucleases / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D016415:Sequence Alignment; D013329:Structure-Activity Relationship
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D004247:DNA; D005090:Exodeoxyribonucleases; C038225:recE protein, E coli