Mechanistic insights into type III restriction enzymes

Raghavendra, Nidhanapati K and Bheemanaik, Shivakumara and Rao, Desirazu N (2012) Mechanistic insights into type III restriction enzymes. In: Frontiers in Bioscience, 17 . pp. 1094-1107.

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Abstract

Type III restriction-modification (R-M) enzymes need to interact with two separate unmethylated DNA sequences in indirectly repeated, head-to-head orientations for efficient cleavage to occur at a defined location next to only one of the two sites. However, cleavage of sites that are not in head-to-head orientation have been observed to occur under certain reaction conditions in vitro. ATP hydrolysis is required for the long-distance communication between the sites prior to cleavage. Type III R-M enzymes comprise two subunits, Res and Mod that form a homodimeric Mod(2) and a heterotetrameric Res(2)Mod(2) complex. The Mod subunit in M-2 or R2M2 complex recognizes and methylates DNA while the Res subunit in R2M2 complex is responsible for ATP hydrolysis, DNA translocation and cleavage. A vast majority of biochemical studies on Type III R-M enzymes have been undertaken using two closely related enzymes, EcoP1I and EcoP15I. Divergent opinions about how the long-distance interaction between the recognition sites exist and at least three mechanistic models based on 1D- diffusion and/or 3D-DNA looping have been proposed.

Item Type:	Journal Article
Publication:	Frontiers in Bioscience
Publisher:	Frontiers in Bioscience
Additional Information:	Copyright of this article belongs to Frontiers in Bioscience.
Keywords:	Restriction-modification system;DNA translocation;ATP hydrolysis;DNA looping;Methyltransferase;Endonuclease;Review
Department/Centre:	Division of Biological Sciences > Biochemistry
Date Deposited:	09 Mar 2012 10:26
Last Modified:	30 Mar 2012 11:31
URI:	http://eprints.iisc.ac.in/id/eprint/43864

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