Artificial virus components: protein polymers that mimick viral capsid proteins

In the development of gene (DNA) therapy, there is a need for suitable components that can ‘package’, target and deliver the therapeutic DNA to the interior of the living cells in the (human) body. In a different application, viz. the development of modern DNA sequencing techniques, components are desired that assist in stretching out the DNA to be sequenced.

With a view to both applications, we are investigating the binding to DNA of ‘protein polymers’ (polymer-like proteins designed from scratch). We use the natural the protein synthesis ‘machinery’ in micro-organisms to create novel protein-like polymers that consist of a string of polymer segments (also called ‘modules’ or blocks), each with a different function, that are often (but not always) inspired by (or copied from) natural proteins.

In order to obtain insight into the parameters that determine the potential suitability of DNA carriers or DNA-stretching agents, a number of interesting and potentially relevant protein polymers should be created, compared and investigated in detail. Possibly, the investigated materials do not only serve as a source of valuable insights. Some of them can be selected in due course for further development towards practical application.

Polymers were created with DNA-binding modules that are rich in positively charged amino acids, and with colloidal stabilizing modules. By design, the stabilizing modules are well soluble in water and assume an essentially random conformation. The polymers, which are synthesised like natural proteins in yeast cells (Pichia pastoris), consist entirely of natural amino acids and can ultimately be fully degraded in the human body. The products were produced at high yield (g/L range), and purified with a cheap & simple procedure.

The polymers bind as a single layer to individual DNA molecules and do not form bridges between the DNA. The complex of polymer and DNA has a shape resembling a cylindrical virus. Novel polymer design will help us to improve and to manipulate the binding.

Project financing

Dutch Polymer Institute (DPI)

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