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Espino-Sanchez TJ, Wienkers H, Marvin RG, Nalder SA, García-Guerrero AE, VanNatta PE, Jami-Alahmadi Y, Blackwell AM, Whitby FG, Wohlschlegel JA, Kieber-Emmons MT, Hill CP, Sigala PA. Direct Tests of Cytochrome Function in the Electron Transport Chain of Malaria Parasites. bioRxiv 2023:2023.01.23.525242. [PMID: 36747727 PMCID: PMC9900762 DOI: 10.1101/2023.01.23.525242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The mitochondrial electron transport chain (ETC) of Plasmodium malaria parasites is a major antimalarial drug target, but critical cytochrome functions remain unstudied and enigmatic. Parasites express two distinct cyt c homologs ( c and c -2) with unusually sparse sequence identity and uncertain fitness contributions. P. falciparum cyt c -2 is the most divergent eukaryotic cyt c homolog currently known and has sequence features predicted to be incompatible with canonical ETC function. We tagged both cyt c homologs and the related cyt c 1 for inducible knockdown. Translational repression of cyt c and cyt c 1 was lethal to parasites, which died from ETC dysfunction and impaired ubiquinone recycling. In contrast, cyt c -2 knockdown or knock-out had little impact on blood-stage growth, indicating that parasites rely fully on the more conserved cyt c for ETC function. Biochemical and structural studies revealed that both cyt c and c -2 are hemylated by holocytochrome c synthase, but UV-vis absorbance and EPR spectra strongly suggest that cyt c -2 has an unusually open active site in which heme is stably coordinated by only a single axial amino-acid ligand and can bind exogenous small molecules. These studies provide a direct dissection of cytochrome functions in the ETC of malaria parasites and identify a highly divergent Plasmodium cytochrome c with molecular adaptations that defy a conserved role in eukaryotic evolution. SIGNIFICANCE STATEMENT Mitochondria are critical organelles in eukaryotic cells that drive oxidative metabolism. The mitochondrion of Plasmodium malaria parasites is a major drug target that has many differences from human cells and remains poorly studied. One key difference from humans is that malaria parasites express two cytochrome c proteins that differ significantly from each other and play untested and uncertain roles in the mitochondrial electron transport chain (ETC). Our study revealed that one cyt c is essential for ETC function and parasite viability while the second, more divergent protein has unusual structural and biochemical properties and is not required for growth of blood-stage parasites. This work elucidates key biochemical properties and evolutionary differences in the mitochondrial ETC of malaria parasites.
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Affiliation(s)
- Tanya J. Espino-Sanchez
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - Henry Wienkers
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - Rebecca G. Marvin
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - Shai-anne Nalder
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - Aldo E. García-Guerrero
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - Peter E. VanNatta
- Department of Chemistry, University of Utah, Salt Lake City, UT, United States
| | - Yasaman Jami-Alahmadi
- Department of Biological Chemistry, University of California, Los Angeles, CA, United States
| | - Amanda Mixon Blackwell
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - Frank G. Whitby
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - James A. Wohlschlegel
- Department of Biological Chemistry, University of California, Los Angeles, CA, United States
| | | | - Christopher P. Hill
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - Paul A. Sigala
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, United States,Corresponding author: Paul Sigala
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