Bioinformatische und biochemische Suche und Identifizierung GPI-verankerter Proteine von Plasmodien, den Erregern der Malaria unter Nutzung einer konditional letalen Hefemutante

Malaria, a parasitosis transmitted by the Apicomplexa family, is still one of the world's most important and dangerous infectious diseases in the 21st century. The eukaryotic parasite is transmitted by the Anopheles mosquito, which is particularly widespread in the tropical and subtropical regions of the world. The course and severity of the disease varies depending on the underlying plasmodial species. Although drug therapy and improved transmission prophylaxis have led to a decline in infections and deaths in recent decades, a significant slowdown in this trend has been observed in recent years, due to the increasing development of resistance to commonly used antiparasitic drugs. In particular, there was also a significant increase in the number of cases during the Covid pandemic. Although a vaccine seems to be available for the first time with RTS,S/AS01 (RTS,S), the search for new therapeutic targets as a basis for the development of an additional therapy is still warranted. Parasite surface proteins bind predominantly by means of a glycosylphosphatidylinositol (GPI) anchor. In addition, free, non-protein-bound GPIs represent important malaria pathogenicity factors. The present work describes the search for additional, previously unknown GPI-anchored proteins in different plasmodial species. With the help of bioinformatic analyses, the proteomes of different plasmodia species were screened for possible GPI-anchored proteins. A structural-descriptive approach was used, based on the distribution of hydrophobic and hydrophilic segments, which is considered typical for GPI-anchored proteins. New, statistically significant candidates were identified in all plasmodial species studied. To substantiate the value of the bioinformatic analysis, a previously unknown GPI candidate protein, PF3D7_1140000, from P. falciparum was selected for stringent molecular and biochemical analyses to provide model validation of the in silico analysis. For this purpose, a conditional lethal yeast mutant was prepared for further studies to analyze whether the plasmodial gene is expressed in yeast as a GPI protein. Furthermore, its expression in yeast with subsequent Triton-X-114 phase separation experiments demonstrated that PF3D7_1140000 is indeed a previously unknown GPI-anchored protein. It is the first GPI-linked enzyme in plasmodia described to date.