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Dissertation
Investigation of Plasmodium falciparum mitochondrial ribosomes
Doctor of Philosophy (Ph.D.), Drexel University
May 2022
DOI:
https://doi.org/10.17918/00001190
Abstract
Mitochondrial ribosomes (mitoribosomes) in different lineages of eukaryotes are vastly divergent with concomitant increase in the number and size of mitoribosomal proteins (MRPs). This is to accommodate variability in the size of mitochondrial rRNA (mt rRNA) encoded in the mitochondrial genome (mtDNA). Plasmodium spp. contains the smallest mtDNA in eukaryotes that encodes only three mitochondrial electron transport chain (mtETC) proteins; COXI, COXIII and cytochrome b (cyt b), where cyt b is a clinically verified antimalarial drug target. Additionally, this mtDNA encodes rRNA genes that are highly fragmented and scrambled with their lengths ranging from 20-200 nucleotides. Current annotations of Plasmodium MRPs are based on sequence similarities with bacterial and eukaryotic systems. This list does not account for the divergent proteins that perform an unparalleled function of gathering fragmented mt rRNA into a functional ribosome. Using 5 small subunit (SSU) and 2 large subunit (LSU) annotated PfMRPs as tools, we have investigated Plasmodium falciparum mitoribosomes. We were the first to report the essentiality of mitoribosomes in apicomplexan parasites by showing that PfMRPL13 knockdown (KD) exhibits abnormalities in mitochondrial morphology and reduces mtETC activity leading to parasite demise. Moreover, total RNA sequencing of PfRSM22 and PfMRPL23 KD parasites show dramatic changes in the parasite transcriptome that has uncovered some aspects of their potential role in mitoribosomal assembly process. Furthermore, we demonstrate formation of a high molecular weight complex at around 0.8MDa formed by all 7 PfMRPs. Mass spectrometry analyses of one SSU protein (PfMRPS18) display necessary features prior to the formation of assembly intermediates. Additionally, with RNA sequencing and mass spectrometry analyses of PfMRPs, we provide a list of proteins of unknown functions having structural similarities with MRPs from other closely related organisms. These attempts highlight only a small fraction of the mitoribosomes in Plasmodium and their deeper understanding is restricted with the long-standing challenge in the field of Plasmodium biology of isolating its mitochondrion with high purity and concentration. Here we discuss the advancements in establishing a possible workflow to isolate Plasmodium mitochondria that will facilitate further investigation of the unconventional mitoribosomes of malaria parasites.
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Details
- Title
- Investigation of Plasmodium falciparum mitochondrial ribosomes
- Creators
- Swati Dass
- Contributors
- Akhil B. Vaidya (Advisor) - Drexel University, Microbiology and ImmunologyHangjun Ke (Advisor) - Drexel University, Microbiology and Immunology
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xvii, 276 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Microbiology and Immunology; College of Medicine; Drexel University
- Other Identifier
- 991018021231204721