THE UBIQUITIN-LIGASE SYSTEM IN TRYPANOSOMA-BRUCEI-BRUCEI

The question of whether the African trypanosome Trypanosoma brucei bru cei utilizes a ubiquitin-ligase system to conjugate the 8,500-dalton p rotein ubiquitin to other proteins has not been investigated. Using I- 125-labeled ubiquitin and gel electrophoresis (sodium dodecyl sulfate and acetic acid, urea, Triton X-100), we looked for the incorporation of label into proteins larger than ubiquitin to determine ubiquitin-li gase system activity in cytosolic and nuclear lysates of long slender, intermediate, and short stumpy bloodstream-form trypanosomes. We pres ent data suggesting that there is cytosolic activity of a ubiquitin-li gase system in all three bloodstream forms of T. brucei brucei. There are indications that the three bloodstream forms of T. brucei brucei d iffer in their cytosolic ubiquitin-ligase system activity. Our assay s howed no activity of this system in the nucleus of T. brucei brucei. F urther studies on the ubiquitin-ligase system in T. brucei brucei may define differences between the three bloodstream forms, the parasite, and its host, leading to development of novel chemotherapeutic strateg ies.