Variations within proteins can now be proven with a greater degree of accuracy by analysing them using mass spectrometry. In a publication in Nature Communications, researchers at Utrecht University describe how they use the method to create an accurate molecular fingerprint of the protein erythropoietin, better known as ‘epo’. This makes it possible to determine the origin of the product, which stimulates the production of red blood cells.
The researchers used a mass spectrometer that was developed in part at Utrecht University, and which provides a more detailed image of the glycosylation of proteins, a natural process in which one or more sugar groups are linked to the protein. The sugar groups determine the protein’s function in the body.
Medication and doping
With the new instrument, the scientists led by Albert Heck, Professor of Biomolecular Mass Spectrometry and Proteomics, were able to study proteins such as epo. Each year, around 10,000 people in the Netherlands use a synthetic variant of this human protein as a medication to treat anaemia. But epo is perhaps better known as a ‘doping’ drug, because of its performance-enhancing properties. As a result, epo is produced for both legal and illegal markets.
The researchers in Utrecht discovered that epo contains more than 250 different combinations of sugar groups. They then used those 250 characteristics to create a molecular fingerprint for the natural variant of epo. They also identified the differences between it and synthetically produced epo from a variety of producers. Each variant has its own unique glycosylation pattern. By identifying that pattern, it is possible to determine where and by whom the synthetic epo was produced. The researchers also developed a ‘biosimilarity’ score to express those differences, which can also be used on other biopharmaceutical proteins.
With the new mass spectrometry method, the researchers also discovered previously unclassified variants of properdin, a protein that plays a role in resistance to pathogens. The new technique may have even broader applications, such as in the development of pharmaceuticals antibodies, as used in cancer- and immune-therapy. It could also be used to conduct research into the differences in glycoproteins - proteins with sugar groups - in the blood of diseased or healthy people. According to the authors of the article, this method for characterising proteins will have an impact on the pharmaceutical industry and on the process of deciding whether to allow biosimilars to the market.
Yang Yang, Fan Liu, Vojtech Franc, Liem Andhyk Halim, Huub Schellekens and Albert J.R. Heck. Hybrid Mass Spectrometry Approaches in Glycoprotein Analysis and their Usage in Scoring Biosimilarity. Nature Communications, 8 Nov. 2016. Doi: 10.1038/ncomms13397