Motoring merozoites: the role of gliding-associated proteins GAP45 and GAP50 in erythrocytic invasion.
Doctoral thesis, UCL (University College London).
A conserved acto-myosin motor complex is implicated in parasite motility and host invasion by a wide variety of Apicomplexan zoites. Until recently, only actin, myosin A (MyoA) and its putative light chain (MLC1 in Toxoplasma gondii) or myosin tail domain interacting protein (MTIP) in Plasmodium spp., had been identified as central to the function of this motor. Identification of two further components in T. gondii, the gliding-associated proteins (GAP45 and GAP50), has provided a valuable insight into how the motor may be anchored in the inner membrane complex (IMC) that lies below the plasma membrane. Results presented here demonstrate that Plasmodium falciparum (Pf)GAP45 and PfGAP50 are expressed and co-localise with PfMTIP at the periphery of merozoites. Both GAPs are found to be in complex with PfMyoA, and PfMTIP. Pulse-chase experiments indicate that the motor complex is assembled in two stages. PfGAP50 is incorporated after the formation of a ternary complex comprising PfGAP45, PfMyoA and PfMTIP. PfGAP45 is shown to be N-myristoylated and palmitoylated and may therefore function as a linker protein tethering the motor to the outer leaflet of IMC. Additionally, PfGAP45 is phosphorylated by calmodulin-dependent protein kinase 1 (CDPK1); a process that may be important in the regulation of the motor. Recombinant PfGAP50 is a well-ordered protein, whereas PfGAP45 has a low content of secondary structure. Potential interaction of GAPs with other motor components has been examined. Co-immunoprecipitation experiments, circular dichroism (CD) and fluorescence spectroscopic analyses have not provided any evidence of direct interaction with any other motor proteins.
|Title:||Motoring merozoites: the role of gliding-associated proteins GAP45 and GAP50 in erythrocytic invasion|
|Additional information:||Pending digitisation|
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