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| Content Provider | World Health Organization (WHO)-Global Index Medicus |
|---|---|
| Author | Kowalczykowski, Stephen C. Yang, Liang Liu, Bian Wigley, Dale B. Handa, Naofumi Dillingham, Mark S. |
| Description | Author Affiliation: Yang L ( Department of Microbiology, University of California, Davis, CA 95616, USA.); |
| Abstract | The RecBCD enzyme is a complex heterotrimeric helicase/nuclease that initiates recombination at double-stranded DNA breaks. In Escherichia coli, its activities are regulated by the octameric recombination hotspot, χ (5'-GCTGGTGG), which is read as a single-stranded DNA sequence while the enzyme is unwinding DNA at over â ¼1,000 bp/s. Previous studies implicated the RecC subunit as the 'χ-scanning element' in this process. Site-directed mutagenesis and phenotypic analyses identified residues in RecC responsible for χ recognition [Handa N, et al., (2012) Proc Natl Acad Sci USA, 10.1073/pnas.1206076109]. The genetic analyses revealed two classes of mutants. Here we use ensemble and single-molecule criteria to biochemically establish that one class of mutants (type 1) has lost the capacity to recognize χ (lost-recognition), whereas the second class (type 2) has a lowered specificity for recognition (relaxed-specificity). The relaxed-specificity mutants still recognize canonical χ, but they have gained the capacity to precociously recognize single-nucleotide variants of χ. Based on the RecBCD structure, these mutant classes define an -helix responsible for χ recognition that is allosterically coupled to a structural latch. When opened, we propose that the latch permits access to an alternative exit channel for the single-stranded DNA downstream of χ, thereby avoiding degradation by the nuclease domain. These findings provide a unique perspective into the mechanism by which recognition of a single-stranded DNA sequence switches the translocating RecBCD from a destructive nuclease to a constructive component of recombinational DNA repair. |
| ISSN | 00278424 |
| e-ISSN | 10916490 |
| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Issue Number | 23 |
| Volume Number | 109 |
| Language | English |
| Publisher | National Academy of Sciences |
| Publisher Date | 2012-06-01 |
| Publisher Place | United States |
| Access Restriction | Open |
| Subject Keyword | DNA Repair Genetics DNA, Single-Stranded Metabolism Escherichia Coli Enzymology Exodeoxyribonuclease V Models, Molecular Regulatory Sequences, Nucleic Acid Physiology Escherichia Coli Proteins Mutagenesis, Site-Directed Protein Structure, Secondary Substrate Specificity Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't Multidisciplinary |
| Content Type | Text |
| Resource Type | Article |
| Subject | Multidisciplinary |
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