Long-range communication of Type III restriction enzymes between their cleavage sites based on ATP-triggered 1D diffusion
Final Report Abstract
In this project we significantly substantiated the diffusion-collision hypothesis for Type III restriction enzymes. In particular, we could show that that these enzymes are rapidly diffusing on DNA without following the pitch of the DNA. Under conditions that support rapid cleavage the enzymes bind first to their target sites using a 3D diffusion mechanism. After binding to the target for some period of time, the enzymes are suddenly switching into the 1D diffusive mode. This switching process requires the hydrolysis of tens of ATPs and causes structural rearrangements of the protein to adopt a long-lived diffusive state. In contrast, no evidence was found that the enzymes hydrolyze ATP during their motion along DNA. ATP hydrolysis by the helicase domains of the enzymes drives thus a conformational change of the protein complex. Such a switching which is not coupled to a directional motion on DNA is a new function for helicases in general. In addition we could demonstrate that diffusion is an integral part of the longrange communication mechanism of these enzymes: When a diffusing enzyme collides with a target site bound enzyme in the correct orientation collision a complex is formed, which cuts DNA on a time scale of seconds.
Publications
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Switching roles for a helicase. Cell Cycle 12, 3125-3126 (2013)
R Seidel, MD Szczelkun
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The helicase-like domains of Type III restriction enzymes trigger long-range diffusion along DNA. Science 340, 353-356 (2013)
FW Schwarz, J Toth, K van Aelst, G Cui, S Clausing, MD Szczelkun, R Seidel
