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BP: Fachverband Biologische Physik
BP 7: Poster I
BP 7.50: Poster
Montag, 23. März 2009, 17:45–20:00, P3
Single-Molecule Studies of DNA Translocating Restriction Enzymes — •Friedrich Schwarz1, Kara van Aelst2, Mark Szczelkun2, and Ralf Seidel1 — 1BIOTEC TU-Dresden Germany — 2University of Bristol, United Kingdom
Restriction enzymes (REs) are the central part of the bacterial defence system against invading viruses. These protein complexes recognize viral DNA by the methylation state of their target sequence and destroy it by cleaving it into pieces. For this, the majority of REs need to interact with two distant target sites. This long-range inter-site communication can be accomplished either by passive 3D diffusive looping or by 1D motion along the DNA contour. Among the different classes of REs, Type I and Type III play a special role due to their helicase domains, which are key to the inter-site communication.
For Type I REs it is established that the helicase domain acts as a dsDNA translocating motor. Cleavage is triggered after a pure 1D communication process, when two translocating motors from distant target sites collide. However details of the actual cleavage-collision process still remain unclear. In comparison, the communication mechanism for Type III REs has not been accurately defined and conflicting models including 3D diffusion and 1D translocation have been proposed. Our recent findings suggest that Type III REs move along DNA by diffusion. In order to explore the cleavage-collision process and to test the diffusion hypothesis we started to track the movement of Type I and III REs along DNA using a setup combining magnetic tweezers with single-molecule fluorescence.