The pro region of Toxoplasma ROP1 is a rhoptry-targeting signal

The rhoptries of Toxoplasma gondii are regulated secretory organelles invol ved in the invasion of host cells. Rhoptry proteins are synthesised as pre- pro-proteins that are processed first to pro-proteins upon entrance into th e secretory pathway, then processed again to their mature forms late in the secretory pathway. The pro-mature processing site of the rhoptry protein R OP1 has been determined, paving the way for understanding the role of the p ro region in rhoptry protein function. We demonstrate here that the ROPI pr o region is sufficient for targeting a reporter protein (amino acids 34-471 of the Trypanosoma brucei VSG 117 protein) to the rhoptries. These results , together with our previous work showing that rhoptry targeting is unaffec ted by deletion of the pro region, indicate that the ROP I protein contains at least two signals that can function in rhoptry targeting. (C) 2001 Aust ralian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.