Protein "bank cells"

Porous protein crystals will allow storing molecules inside cells

Sofia Dolotovskaya, N+1

Japanese bioengineers have developed protein crystals with a porous structure capable of holding exogenous molecules inside living cells. In the future, such porous crystals can be used, for example, for intracellular delivery of drugs or enzymes. The article was published in the journal ACS Nano (Abe et al., Crystal Engineering of Self-Assembled Porous Protein Materials in Living Cells).

The prototype for protein crystals was the protein shell of cypoviruses that cause polyhedrosis in insects. These viruses are enclosed in polyhedral protective protein crystals called polyhedra and have very high stability. This stability is ensured by the dense packing of polyhedrine monomers into trimers, which form a crystal with low porosity, limiting the inclusion of foreign molecules.

(Here and below are the pictures from the article in ACS Nano).

The authors suggested that increasing the porosity of the polyhedrine crystal while maintaining its stability would allow it to be used for capturing and storing exogenous molecules in living cells. To increase porosity, scientists used genetic engineering methods to remove amino acid residues located on the contact surface of each trimer. This made it possible to preserve the original structure of the crystal lattice, but at the same time increase the pore size.

Scheme of obtaining porous protein crystals

The resulting mutant protein crystals with a size of several microns are able to adsorb 2-4 times more exogenous molecules than wild-type polyhedra. They also have the ability to strongly concentrate molecules: for example, the fluorescent paint from the solution was concentrated in crystals 5 thousand times.

Scientists have also traced how mutant crystals behave inside living insect cells. The crystals turned out to be very stable and able to accumulate paint right inside the cells.

The study opens up prospects for the development of nanomaterials with controlled porosity from natural self-organizing protein crystals. Such porous crystals can be used, for example, for intracellular delivery of drugs or enzymes. Protein pores can also be used for structural analysis of cellular molecules by crystallization.

Crystallization is one of the main methods of studying the structure of membrane proteins. Large protein crystals are studied using X-ray crystallography methods, which make it possible to determine their molecular structure very accurately from the radiation scattering pattern. Recently, another group of Japanese scientists described the crystallization of photosensitive membrane proteins of bacteriorhodopsins. It turned out that during crystallization they behave like "cannibals": the growth of large crystals occurs due to the "devouring" of smaller crystals around them.

Portal "Eternal youth" http://vechnayamolodost.ru  09.02.2017