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Originally published as MBC in Press, 10.1091/mbc.E07-01-0040 on May 30, 2007

Vol. 18, Issue 8, 3039-3046, August 2007

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Immobilization of the Type XIV Myosin Complex in Toxoplasma gondiiFormula

Terezina M. Johnson, Zenon Rajfur, Ken Jacobson, and Con J. Beckers

Department of Cell and Developmental Biology, The University of North Carolina, Chapel Hill, NC 27599-7090

Submitted January 18, 2007; Revised May 14, 2007; Accepted May 18, 2007
Monitoring Editor: Yu-li Wang

The substrate-dependent movement of apicomplexan parasites such as 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. For the interaction of this complex with F-actin to result in net parasite movement, it is necessary that the myosin be immobilized with respect to the parasite and the actin 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 seem to be accomplished by direct interactions with cytoskeletal elements. Immobilization of the motor complex, however, does seem to require cholesterol. 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 such as Plasmodium and possibly to other eukaryotes.

This was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E07-01-0040) on May 30, 2007.

Formula The online version of this article contains supplemental material at MBC Online (http://www.molbiolcell.org).

Address correspondence to: Con J. Beckers (cbeckers{at}med.unc.edu).

Abbreviations used: CE, cholesteryl; DRM, detergent-resistant membrane; FRAP, fluorescence recovery after photobleaching; IMC, inner membrane complex; mbetaCD, methyl-beta-cyclodextrin; PC, phosphocholine; TLC, thin layer chromatography.




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