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DNA looping and translocation provide an optimal cleavage mechanism for the type III restriction enzymes

Crampton, Neal and Roes, Stefanie and Dryden, David TF and Rao, Desirazu N and Edwardson, J Michael and Henderson, Robert M (2007) DNA looping and translocation provide an optimal cleavage mechanism for the type III restriction enzymes. In: EMBO Journal, 26 (16). 3815 -3825.

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Official URL: http://www.nature.com/emboj/journal/v26/n16/abs/76...

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.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Nature Publishing Group.
Department/Centre: Division of Biological Sciences > Biochemistry
Date Deposited: 10 Jun 2010 10:27
Last Modified: 10 Jun 2010 10:27
URI: http://eprints.iisc.ernet.in/id/eprint/26160

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