Throwing a chemical spanner in the malaria invasion motor: Interaction and dynamics of the Plasmodium MTIP/MyoA complex
Author(s)
Thomas, Jemima Carys
Type
Thesis
Abstract
Malaria kills over one million people per year and has devastating social and economic
effects on endemic countries. It is caused by the Plasmodium parasite which has a history of
developing resistance to anti-malarial drugs, meaning new therapeutics are urgently required.
A key event in the Plasmodium life cycle is the invasion of human erythrocytes. The force for
this invasion is derived from an actomyosin motor located inside the parasite plasma
membrane. This molecular motor consists of a type XIV myosin, Myosin A (MyoA), bound
to myosin tail interacting protein (MTIP). The MTIP/MyoA protein-protein interaction is a
potential anti-malarial drug target; disruption of this complex should stall erythrocyte
invasion and kill the parasite.
In the work discussed in this thesis the MyoA tail was mimicked using short chain peptides
for the study of MTIP/MyoA binding in vitro. Development of fluorescence assays for the
analysis of MyoA peptide binding to MTIP and the screening of potential inhibitors of this
complex is described, together with the application of these assays to identify novel binding
motifs at the MTIP/MyoA interface. In combination with peptide arrays, these fluorescence
assays were also used to investigate MTIP binding to Myosin B (MyoB), another
Plasmodium myosin of unknown function. No binding partners of MyoB have yet been
identified in vivo, but results reported here show that MTIP can bind MyoB peptides in vitro.
CD spectroscopy and protein NMR experiments were used to investigate the structures of
MTIP/MyoA and MTIP/MyoB peptide complexes in solution, and indicate that MTIP
undergoes a large conformational change upon myosin peptide binding. These structural
techniques together with the fluorescence assays provide a platform for future drug discovery
efforts targeting MTIP/MyoA.
Finally, the information obtained concerning the MTIP/MyoA interaction was used to design
and synthesise α-helix mimetic compounds of MyoA. These compounds were examined for
inhibition activity against MTIP/MyoA using fluorescence assays, and appear to be able to
disrupt MTIP/MyoA complex formation in vitro. This provides a starting point for future
anti-malarial drug development and is a further step towards the chemical validation of
MTIP/MyoA as a drug target.
effects on endemic countries. It is caused by the Plasmodium parasite which has a history of
developing resistance to anti-malarial drugs, meaning new therapeutics are urgently required.
A key event in the Plasmodium life cycle is the invasion of human erythrocytes. The force for
this invasion is derived from an actomyosin motor located inside the parasite plasma
membrane. This molecular motor consists of a type XIV myosin, Myosin A (MyoA), bound
to myosin tail interacting protein (MTIP). The MTIP/MyoA protein-protein interaction is a
potential anti-malarial drug target; disruption of this complex should stall erythrocyte
invasion and kill the parasite.
In the work discussed in this thesis the MyoA tail was mimicked using short chain peptides
for the study of MTIP/MyoA binding in vitro. Development of fluorescence assays for the
analysis of MyoA peptide binding to MTIP and the screening of potential inhibitors of this
complex is described, together with the application of these assays to identify novel binding
motifs at the MTIP/MyoA interface. In combination with peptide arrays, these fluorescence
assays were also used to investigate MTIP binding to Myosin B (MyoB), another
Plasmodium myosin of unknown function. No binding partners of MyoB have yet been
identified in vivo, but results reported here show that MTIP can bind MyoB peptides in vitro.
CD spectroscopy and protein NMR experiments were used to investigate the structures of
MTIP/MyoA and MTIP/MyoB peptide complexes in solution, and indicate that MTIP
undergoes a large conformational change upon myosin peptide binding. These structural
techniques together with the fluorescence assays provide a platform for future drug discovery
efforts targeting MTIP/MyoA.
Finally, the information obtained concerning the MTIP/MyoA interaction was used to design
and synthesise α-helix mimetic compounds of MyoA. These compounds were examined for
inhibition activity against MTIP/MyoA using fluorescence assays, and appear to be able to
disrupt MTIP/MyoA complex formation in vitro. This provides a starting point for future
anti-malarial drug development and is a further step towards the chemical validation of
MTIP/MyoA as a drug target.
Date Issued
2011-05
Date Awarded
2011-07
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Tate, Ed
Creator
Thomas, Jemima Carys
Grant Number
EPSRC, MRC, Royal Society
Publisher Department
Chemistry
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)