Mapping DNA – Lac repressor interaction with ultra-fast optical tweezers
Authors: Monico C., Tempestini A., Vanzi F., Pavone FS., Capitanio M.
Autors Affiliation: Univ Oxford, Chem Res Lab, Oxford OX1 2JD, England; LENS European Lab Nonlinear Spect, I-50019 Sesto Fiorentino, Italy; Univ Florence, Dept Phys & Astron, I-50019 Sesto Fiorentino, Italy; Univ Florence, Dept Evolutionary Biol, I-50125 Florence, Italy; CNR, Natl Inst Opt, I-50125 Florence, Italy; Int Ctr Computat Neurophoton, I-50019 Sesto Fiorentino, FI, Italy
Abstract: The lac operon is a well-known example of gene expression regulation, based on the specific interaction of Lac repressor protein (LacI) with its target DNA sequence (operator). We recently developed an ultrafast force-clamp laser trap technique capable of probing molecular interactions with sub-ms temporal resolution, under controlled pN-range forces. With this technique, we tested the interaction of LacI with different DNA constructs. Based on position along the DNA sequence, the observed interactions can be interpreted as specific binding to operator sequences and transient interactions with nonspecific sequences.
KeyWords: optical tweezers; single-molecule biophysics; force spectroscopy; protein-DNA interactions; lac repressor; facilitated-diffusion model