The diphthamide biomolecule is essential for the proper formation of proteins in cells. When humans are infected with diphtheria, diphthamide is altered by diphtheria toxin, so life-threatening complications can occur from altered protein formation. Until now, diphthamide was only known from animals and fungi. A research team has just demonstrated that the biomolecule is also present in plants.
Researchers have also shown that its formation can be affected by certain environmental factors. This was published in the journal Nature Communication, July 11, 2022.
The study was carried out in the department of Ute Krämer, with contributions from the research group of Prof. Raffael Schaffrath of the University of Kassel and Prof. Lorenz Adrian of the Technical University of Berlin, as well as other groups research in Germany.
Plants without diphthamide grow less
The diphthamide biomolecule is a natural modification of the so-called elongation factor 2 protein of many organisms. This protein is one of the components responsible for building all the proteins in the cell. “This modification has long been known to be the target of diphtheria toxin, which can lead to life-threatening complications in people infected with diphtheria by preventing cellular protein synthesis,” explains Ute Krämer. “Diphtheria infections of bacterial origin have been documented since ancient times and were greatly feared until the 19th century, before a vaccine was developed.”
Until now, diphthamide had only been identified and studied in detail in animal organisms and baker’s yeast – as a model organism for medical research. Ute Krämer’s team has now shown that diphthamide also forms in plants and fulfills an important function: if the ability to form diphthamide is absent in the plant, there is an increased error rate in the biosynthesis. proteins. Additionally, plant growth is reduced due to decreased cell division. Several additional alterations in central cellular regulatory processes could contribute to causing growth restriction.
Stress influences the formation of diphthamide
According to the results of the study, the essential initial step of diphthamide biosynthesis known to mammals and yeasts also takes place in plants. Therefore, it is likely that this is also the case for the later steps leading to the diphthamide now detected in plants. “What is completely new, however, is that not only genetic defects can lead to diphthamide loss,” explains Ute Krämer. “Environmental stress, particularly an excess of the trace nutrient copper or the environmental toxin cadmium, also inhibits diphthamide formation in plants.” In the presence of high concentrations of copper, human cells also showed diphthamide deficiency. These results identify a new factor influencing plant growth rates, and they could also contribute to a better understanding of how diseases develop. “It must now be investigated whether plant pathogens also use diphthamide as an Achilles’ heel, just as the diphtheria pathogen does in humans,” says Ute Krämer.
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