Proteolytic processing of TgIMC1 during maturation of the membrane skeleton of Toxoplasma gondii.
Membrane skeletons play an important role in the maintenance of cell shape and integrity in many cell types. In the protozoan parasite Toxoplasma gondii this function is performed by the subpellicular network, a resilient structure composed of tightly interwoven 10-nm filaments. We report here that this network is assembled at an early stage in the development of daughter parasites. The networks of immature and mature parasites differ dramatically with respect to their stability. Although in immature parasites the network is completely solubilized by detergent, the network in mature parasites is entirely detergent-resistant. Conversion of the detergent-labile to the detergent-resistant network occurs late in daughter cell development and appears to be coupled to proteolytic processing of the carboxyl terminus of TgIMC1, the major subunit of the network filaments. A single cysteine residue in the TgIMC1 carboxyl terminus was found to be essential for this processing event. The dramatic change in resistance to detergent extraction probably reflects an overall change in structural stability of the subpellicular network that accompanies maturation of daughter parasites and allows a switch from an assembly-competent but loose structure to one that is rigid and offers mechanical strength to the mature parasite.
Mann
Tara
T
Division of Geographic Medicine, University of Alabama at Birmingham, 845 19th Street South, Birmingham, AL 35294-2170, USA.
Gaskins
Elizabeth
E
Beckers
Con
C
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers; D006868:Hydrolysis; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011499:Protein Processing, Post-Translational; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014122:Toxoplasma / Q000254:growth & development / Q000378:metabolism*
D003598:Cytoskeletal Proteins; D017931:DNA Primers; C435912:IMC1 protein, Toxoplasma gondii; D015800:Protozoan Proteins