Using DNA, scientists organized bioactive proteins in desired 2D and 3D ordered arrays — promising for structural biology, biomedicine, and more.
«For decades, scientists have dreamed about rationally assembling proteins into specific organizations with preserved protein function,» said corresponding author Oleg Gang, leader of the Center for Functional Nanomaterials (CFN) Soft and Bio Nanomaterials Group at Brookhaven Lab and a professor of chemical engineering and of applied physics and materials science at Columbia Engineering. «Our DNA-based platform has enormous potential not only for structural biology but also for various bioengineering, biomedical, and bionanomaterial applications.»
The primary motivation of this work was to establish a rational way to organize proteins into designed 2-D and 3-D architectures while preserving their function. The importance of organizing proteins is well known in the field of protein crystallography. For this technique, proteins are taken from their native solution-based environments and condensed to form an orderly arrangement of atoms (crystalline structure), which can then be structurally characterized. However, because of their flexibility and aggregation properties, many proteins are difficult to crystallize, requiring trial and error. The structure and function of proteins may change during the crystallization process, and they may become nonfunctional when crystallized by traditional methods. This new approach opens many possibilities for creating engineered biomaterials, beyond the goals of structural biology.
«The ability to make biologically active protein lattices is relevant to many applications, including tissue engineering, multi-enzyme systems for biochemical reactions, large-scale profiling of proteins for precision medicine, and synthetic biology,» added first author Shih-Ting (Christine) Wang, a postdoc in the CFN Soft and Bio Nanomaterials Group.
Though DNA is best known for its role in storing our genetic information, the very same base-pairing processes used for this storage can be leveraged to construct desired nanostructures. A single strand of DNA is made of subunits, or nucleotides, of which there are four kinds (known by the letters A, C, T, and G). Each nucleotide has a complementary nucleotide it attracts and binds to (A with T and C with G) when two DNA strands are near each other. Using this concept in the technique of DNA origami, scientists mix multiple short strands of synthetic DNA with a single long strand of DNA. The short strands bind to and «fold» the long strand into a particular shape based on the sequence of bases, which scientists can specify.
In this case, the scientists created octahedral-shaped DNA origami. Inside these cage-like frameworks, they placed DNA strands with a particular «color,» or coding sequence, at targeted locations (center and off center). To the surface of proteins — specifically, ferritin, which stores and releases iron, and apoferritin, its iron-free counterpart — they attached complementary DNA strands. By mixing the DNA cages and conjugated proteins and heating up the mixture to promote the reaction, the proteins went to the internal designated locations. They also created empty cages, without any protein inside.
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Materials provided by DOE/Brookhaven National Laboratory. Note: Content may be edited for style and length.