PMID:17660745
| Citation |
Crampton, N, Roes, S, Dryden, DT, Rao, DN, Edwardson, JM and Henderson, RM (2007) DNA looping and translocation provide an optimal cleavage mechanism for the type III restriction enzymes. EMBO J. 26:3815-25 |
|---|---|
| Abstract |
EcoP15I is a type III restriction enzyme that requires two recognition sites in a defined orientation separated by up to 3.5 kbp to efficiently cleave DNA. The mechanism through which site-bound EcoP15I enzymes communicate between the two sites is unclear. Here, we use atomic force microscopy to study EcoP15I-DNA pre-cleavage complexes. From the number and size distribution of loops formed, we conclude that the loops observed do not result from translocation, but are instead formed by a contact between site-bound EcoP15I and a nonspecific region of DNA. This conclusion is confirmed by a theoretical polymer model. It is further shown that translocation must play some role, because when translocation is blocked by a Lac repressor protein, DNA cleavage is similarly blocked. On the basis of these results, we present a model for restriction by type III restriction enzymes and highlight the similarities between this and other classes of restriction enzymes. |
| Links |
PubMed PMC1952222 Online version:10.1038/sj.emboj.7601807 |
| Keywords |
Adenosine Triphosphate/analogs & derivatives; Adenosine Triphosphate/metabolism; DNA/chemistry; DNA/metabolism; Deoxyribonucleases, Type III Site-Specific/genetics; Deoxyribonucleases, Type III Site-Specific/metabolism; Macromolecular Substances; Microscopy, Atomic Force; Models, Molecular; Nucleic Acid Conformation; Repressor Proteins/metabolism |
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