TITLE: "Exploring the dynamic interaction between DNA and proteins at a single molecule level"

SPEAKER: Professor Gijs J. L. Wuite

Single-molecule experiments have proved to be very suitable to obtain dynamic information on proteins and protein-DNA interactions. In particular optical tweezers have been applied in such studies since they are able to probe at piconetwon force scale and nanometer length scale which is a typical range for the function of many DNA-enzymes. For example, we have used this technique to elucidate the cutting reaction of restriction enzymes. Restriction enzymes recognize specific base sequences of dsDNA and cleave the DNA strand at such sites. The specificity of these enzymes is the result of a large conformational change in the enzyme and/or DNA triggered by the correct site. Restriction enzymes have proven to be a superb model system to study highly specific protein-DNA interactions. We measured the effect of DNA tension on the cleavage activity of restriction enzymes (BamHI and EcoRV). From these experiments we have been able to develop a model that explains the different energetic contributions of the DNA tension on the reaction speed. This allowed us to accurately predict the bending angle of DNA due to enzyme binding, as well as to obtain various hard to measure reaction rates of the restriction reaction.