Creator organelles in living mammalian cells can generate synthetic proteins

A research team led by Professor Edward Lemke, a biophysical chemist, has developed a designer organelle in a living mammalian cell according to a new process of complex biological translation. The organelle created without a membrane can generate proteins from natural and synthetic amino acids carrying new features. For example, scientists could incorporate fluorescent building blocks into proteins via the organelle, thereby visualizing the interior of the cell with the help of imaging methods. Research work now published in Science was a collaboration of the Johannes Gutenberg University of Mainz (JGU), the Institute of Molecular Biology (IMB) and the European Molecular Biology Laboratory (EMBL).

Organelles are compartments in cells that, like the nucleus or mitochondria, perform specific functions. The Lemke group has created a new compartment in which special proteins can be synthesized. "In a figurative sense, we look for a corner in the cell where we build our house, and then we import some of the ribosomes in the cell," said Professor Edward Lemke. Protein biosynthesis takes place at the level of ribosomes. By using the genetic code, messenger RNA (mRNA) is translated into the amino acid sequence of the protein to be formed.

Translation is a very complex process that can not be easily contained in an organelle surrounded by a membrane. As a result, Lemke's team was inspired by the creation of the designer organelle from phase separation, that is, from the process responsible for membrane-free organelle formation. in vivosuch as nucleoli or stress granules. The cells use phase separation to locally concentrate specific proteins and RNAs, as well as to create new compartments without membrane. "Our membraneless organelle is practically an open reaction center," said Lemke.

This allows the biosynthesis of proteins to take place in a well-defined place, which is important for working with synthetic amino acids. Researchers have already been able to create a new protein with the help of an unnatural synthetic amino acid. However, nonspecific incorporation of the protein into the cell causes high cellular stress and the cell can be severely affected. The new orthogonal translation method avoids this problem.

Large pool of natural and synthetic amino acids for protein synthesis on designer organelles

"Our organelle can make proteins using non-canonical synthetic amino acids, at present we know more than 300 different non-canonical amino acids – compared with 20 natural ones. more limited to these ", Gemma Estrada Girona, who, with Christopher Reinkemeier, is the first author of the Science paper. Human proteins are made up of 20 natural canonical amino acids. In addition, there are a number of non-canonical amino acids, which are not found in normal human proteins. However, the extension of the genetic code allows the incorporation of these non-canonical amino acids and the new organelle designer is able to expand the genetic code selectively. This translates RNA differently in the organelle than in the rest of the cell. "We took nature as a model, particularly the membrane-free nucleolus, which participates in the synthesis of RNA in the nucleus," said Lemke. "We were surprised to be able to build such a complicated structure and function in just a few steps."

The new concept could serve as a platform for the design of other organelles and the construction of semi-synthetic cells and organisms. "Our tool can also be used to design translation and perhaps other cellular processes such as transcription and post-translational modifications.This could even allow us to design new types of organelles that expand the functional repertoire of complex living systems, "said Christopher Reinkemeier. .

The designer organelles combine the fields of biology and chemistry to create a whole new feature. One of the areas of application is the aforementioned fluorescence imaging method, another could be the production of antibodies for therapeutic purposes. First and foremost, Lemke and his group aim to design minimal designer organelles to minimize the impact on the body's healthy physiology.

Edward Lemke is a visiting group leader at the European Molecular Biology Laboratory, Professor of Synthetic Biophysics at the Johannes Gutenberg University in Mainz and Deputy Director at the Institute of Molecular Biology. He is also coordinating the new priority program "Molecular Mechanisms of Functional Phase Separation" (SPP 2191), funded by the German Research Foundation.