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Materials

Viral Coat Protein Guides Self-Assembly

Shape of viruslike particle depends on the length of a silklike block in the middle of the protein

by Celia Henry Arnaud
September 1, 2014 | A version of this story appeared in Volume 92, Issue 35

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Credit: Nat. Nanotechnol.
This viral coat protein consists of a DNA-binding oligolysine segment (red), a silklike block that drives self-assembly (magenta), and a random coil that prevents aggregation (green).
A cartoon of a triblock minimal coat protein for artificial viruses, showing the oligolysine block (red), the silk-like block (magenta), and the random coil block (green)
Credit: Nat. Nanotechnol.
This viral coat protein consists of a DNA-binding oligolysine segment (red), a silklike block that drives self-assembly (magenta), and a random coil that prevents aggregation (green).

Artificial viruses have potential uses as DNA-based drug delivery particles and structural materials. But scientists find it difficult to make artificial viruses that self-assemble with the same ease as natural viruses. Researchers led by Armando Hernandez-Garcia and Renko de Vries of Wageningen University, in the Netherlands, have made progress toward that goal with a viral coat protein that self-assembles with DNA in a way that mimics the tobacco mosaic virus (Nat. Nanotechnol. 2014, DOI: 10.1038/nnano.2014.169). The protein consists of three distinct blocks: an oligolysine that binds DNA, a silklike sequence that folds into thick filaments, and a hydrophilic random coil that prevents virus particle aggregation. By varying the length of the silklike block from zero to 14 repeat units, the researchers tune the shape of the particles. With shorter silk blocks, the protein simply coats the DNA. With longer silk blocks of 10 or more repeat units, the protein and DNA cooperatively self-assemble to form rod-shaped particles. The researchers show that these viruslike particles can enter cells and protect the DNA from degradation.

Five panels showing the different morphologies adopted when coat proteins with silk blocks of different length self-assemble with DNA.
Credit: Nat. Nanotechnol.
The morphology of viruslike particles depends on the length of the silklike middle block; the proteins here contain (from left) zero, two, four, 10, or 14 repeat units in the silk block.

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