Ns. Morrissette et al., SUBPELLICULAR MICROTUBULES ASSOCIATE WITH AN INTRAMEMBRANOUS PARTICLELATTICE IN THE PROTOZOAN PARASITE TOXOPLASMA-GONDII, Journal of Cell Science, 110, 1997, pp. 35-42
Application of Fourier analysis techniques to images of isolated, froz
en-hydrated subpellicular microtubules from the protozoan parasite Tox
oplasma gondii demonstrates a distinctive 32 nm periodicity along the
length of the microtubules, A 32 nm longitudinal repeat is also observ
ed in the double rows of intramembranous particles seen in freeze-frac
ture images of the parasite's pellicle; these rows are thought to over
lie the subpellicular microtubules. Remarkably, the 32 nm intramembran
ous particle periodicity is carried over laterally to the single rows
of particles that lie between the microtubule-associated double rows.
This creates a two-dimensional particle lattice, with the second dimen
sion at an angle of similar to 75 degrees to the longitudinal rows (de
pending on position along the length of the parasite). Drugs that disr
upt known cytoskeletal components fail to destroy the integrity of the
particle lattice. intramembranous particle organization suggests exis
tence of multiple cytoskeletal filaments of unknown identity. Filament
s associated with the particle lattice provide a possible mechanism fo
r motility and shape change in Toxoplasma: distortion of the lattice m
ay mediate the twirling motility seen upon host-cell lysis, and morpho
logical changes observed during invasion.