Tubulin biosynthesis in the developmental cycle of a parasitic protozoan, Leishmania mexicana: changes during differentiation of motile and nonmotile stages.

Cytodifferentiation in the transition cycle of the parasitic protozoan Leishmania mexicana amazonensis was studied in vitro. The flagellated motile promastigotes transform into the nonmotile amastigotes in 7 days at 35 degrees C intracellularly in the murine macrophage line J774G8. In medium 199 plus fetal bovine serum, the reverse transformation occurs extracellularly at 27 degrees C in 2 days. Slab gel electrophoresis of leishmanias labeled with [35S]methionine during transformation revealed changes in protein banding patterns. The intensity of two protein species with apparent molecular weights of approximately equal to 55,000 increased in the amastigote-to-promastigote differentiation and decreased during the reverse transformation. These two protein species comigrated approximately with alpha- and beta-tubulin of Chlamydomonas flagella in two-dimensional gel electrophoresis. The lower band was further identified as beta-tubulin by immunoprecipitation using rabbit antiserum specific to the beta-tubulin of Chlamydomonas axonemes. The biosynthetic change of tubulin was found to correlate with the morphological change of microtubules is leishmanial flagella and cytoskeleton during transformation.