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Dissertation
Identification of the myosin B light chain partner in Plasmodium and elucidation of the motor properties
Doctor of Philosophy (Ph.D.), Drexel University
Apr 2011
DOI:
https://doi.org/10.17918/00000601
Abstract
Apicomplexans are obligate intracellular parasites that depend on an actin-myosin motor system located beneath the plasma membrane of invasive stages for host cell invasion and gliding motility. For Plasmodium , components of the essential myosin motor participating in this function include MyoA, a type XIV myosin heavy chain and its light chain MTIP, which interacts with the myosin via the extreme carboxy-terminal residues of MyoA as originally defined by the yeast two hybrid system. Little is known regarding the components or functions of the other Plasmodium myosins. MyoB is a second type XIV myosin of Plasmodium, which is 35% identical and 59% similar to MyoA, but interestingly amino acid sequence comparisons suggest that this myosin may be Plasmodium specific. An Y2H assay has identified a novel MyoB tail interacting protein, designated as MTIP-B. Sequence alignment studies have shown that MTIP-B is distantly related to MTIP and BLAST analysis has indicated that MTIP-B is also Plasmodium-specific. Knock out attempts have been unsuccessful, suggesting that the motor is essential. Stage-specific expression profile studies have shown that the expressions of MTIP-B and MyoB peak during late blood stages. This implies an important function for this motor during that period. Localization studies performed using GFP-tagged PfMTIP-B parasites have revealed an interesting punctate distribution of the protein throughout the parasite cell during late stages. Both myosin proteins were found to be resistant to complete extraction even under very stringent conditions, suggesting them to be tightly associated with an insoluble fraction in the cell. We believe that this fraction also represents the actual cellular site of action of this motor. Furthermore, Blue-native PAGE analysis identified a ~450 kDa complex in the soluble parasite extract, suggesting the presence of additional components associated with the motor. A functional conditional knockdown system has enabled us to regulate the expression of MTIP-B, thus providing a system to possibly knock out the essential endogenous copy for investigating the functional aspects of this protein. We believe that the myosin B motor plays a critical and novel role in Plasmodium, the nature of which, once determined, will be extremely significant in employing approaches for containment of disease progression in the symptomatic stage of the parasite.
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Details
- Title
- Identification of the myosin B light chain partner in Plasmodium and elucidation of the motor properties
- Creators
- Kasturi Chatterjee
- Contributors
- Lawrence W. Bergman (Advisor)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xvi, 143 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Microbiology and Immunology; College of Medicine; Drexel University
- Other Identifier
- 991014970336404721