High-resolution structures of malaria parasite actomyosin and actin filaments

Malaria is responsible for half a million deaths annually and poses a huge economic burden on the developing world. The mosquito-borne parasites ( spp.) that cause the disease depend upon an unconventional actomyosin motor for both gliding motility and host cell invasion. The motor system, often referred to as the glideosome complex, remains to be understood in molecular terms and is an attractive target for new drugs that might block the infection pathway. Here, we present the first high-resolution structure of the actomyosin motor complex from . Our structure includes the malaria parasite actin filament (Act1) complexed with the myosin motor (MyoA) and its two associated light-chains. The high-resolution core structure reveals the Act1:MyoA interface in atomic detail, while at lower-resolution, we visualize the MyoA light-chain binding region, including the essential light chain (ELC) and the myosin tail interacting protein (MTIP). Finally, we report a bare Act1 filament structure at an improved resolution, which gives new information about the nucleotide-binding site, including the orientation of the ATP/ADP sensor, Ser15, and the presence of a channel, which we propose as a possible phosphate exit path after ATP hydrolysis.