title: Protein-DNA chimeras for single molecule mechanical folding studies with the optical tweezers.
abstract: Here we report on a method that extends the study of the mechanical behavior of single proteins to the low force regime of optical tweezers. This experimental approach relies on the use of DNA handles to specifically attach the protein to polystyrene beads and minimize the non-specific interactions between the tethering surfaces. The handles can be attached to any exposed pair of cysteine residues. Handles of different lengths were employed to mechanically manipulate both monomeric and polymeric proteins. The low spring constant of the optical tweezers enabled us to monitor directly refolding events and fluctuations between different molecular structures in quasi-equilibrium conditions. This approach, which has already yielded important results on the refolding process of the protein RNase H (Cecconi et al. in Science 309: 2057-2060, 2005), appears robust and widely applicable to any protein engineered to contain a pair of reactive cysteine residues. It represents a new strategy to study protein folding at the single molecule level, and should be applicable to a range of problems requiring tethering of protein molecules.
authors.affiliation: Department of Molecular and Cell Biology, Institute for Quantitative Biology, University of California - Berkeley, Berkeley, CA 94720-3220, USA.
authors.forename: Ciro
authors.initials: C
authors.lastname: Cecconi
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Shank
authors.forename: Frederick W
authors.initials: FW
authors.lastname: Dahlquist
authors.forename: Susan
authors.initials: S
authors.lastname: Marqusee
authors.forename: Carlos
authors.initials: C
authors.lastname: Bustamante
mesh_terms: D003198:Computer Simulation; D004247:DNA / Q000737:chemistry* / Q000648:ultrastructure*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D008846:Micromanipulation / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D015336:Molecular Probe Techniques; D052898:Optical Tweezers; D011487:Protein Conformation; D017510:Protein Folding; D013314:Stress, Mechanical
chemical_list: D004268:DNA-Binding Proteins; D004247:DNA