Precise Coating of a Wide Range of DNA Templates by a Protein Polymer with a DNA Binding Domain

Emerging DNA-based nanotechnologies would benefit from the ability to modulate the properties (e.g., solubility, melting temperature, chemical stability) of diverse DNA templates (single molecules or origami nanostructures) through controlled, self-assembling coatings. We here introduce a DNA coating agent, called C8–BSso7d, which binds to and coats with high specificity and affinity, individual DNA molecules as well as folded origami nanostructures. C8–BSso7d coats and protects without condensing, collapsing or destroying the spatial structure of the underlying DNA template. C8–BSso7d combines the specific nonelectrostatic DNA binding affinity of an archeal-derived DNA binding domain (Sso7d, 7 kDa) with a long hydrophilic random coil polypeptide (C8, 73 kDa), which provides colloidal stability (solubility) through formation of polymer brushes around the DNA templates. C8–BSso7d is produced recombinantly in yeast and has a precise (but engineerable) amino acid sequence of precise length. Using electrophoresis, AFM, and fluorescence microscopy we demonstrate protein coat formation with stiffening of one-dimensional templates (linear dsDNA, supercoiled dsDNA and circular ssDNA), as well as coat formation without any structural distortion or disruption of two-dimensional DNA origami template. Combining the programmability of DNA with the nonperturbing precise coating capability of the engineered protein C8–BSso7d holds promise for future applications such as the creation of DNA–protein hybrid networks, or the efficient transfection of individual DNA nanostructures into cells.