Mol Biol Cell. 2007 May 30; [Epub ahead of print]
Immobilization of the Type XIV Myosin Complex in Toxoplasma gondii
Johnson TM, Rajfur Z, Jacobson K, Beckers CJ.
Department of Cell and Developmental Biology, The University of North Carolina, Chapel Hill, NC 27599-7090.
Monitoring Editor: Yu-li Wang The substrate-dependent movement of apicomplexan parasites like Toxoplasma gondii and Plasmodium sp. is driven by the interaction of a type XIV myosin with F-actin. A complex containing the myosin-A heavy chain, a myosin light chain and the accessory protein GAP45 is attached to the membranes of the inner membrane complex (IMC) through its tight interaction with the integral membrane glycoprotein GAP50. In order for the interaction of this complex with F-actin to result in net parasite movement, it is necessary that one of them be immobilized with respect to the parasite and the other with respect to the substrate the parasite is moving on. We report here that the myosin motor complex of Toxoplasma is firmly immobilized in the plane of the IMC. This does not appear to be accomplished by direct interactions with cytoskeletal elements. Immobilization of the motor complex does appear to require cholesterol, however. Both the motor complex and the cholesterol are found in detergent-resistant membrane domains that encompass a large fraction of the inner membrane complex surface. The observation that the myosin XIV motor complex of Toxoplasma is immobilized within this cholesterol-rich membrane likely extends to closely related pathogens like Plasmodium and possibly other eukaryotes.
PMID: 17538016 [PubMed - as supplied by publisher]