THE DNAJ FAMILY OF PROTEIN CHAPERONES IN TRYPANOSOMA-CRUZI

We have molecularly cloned four members of the DnaJ (heat shock protei n 40) family of protein chaperones of the protozoan parasite Trypanoso ma cruzi-tcj1, tcj2, tcj3 and tcj4. While all the proteins contain def ining J domains at their N-termini, only tcj2, tcj3 and tcj4 contain g lycine/phenylalanine-rich and zinc finger domains common to many other DnaJ homologues. Furthermore, tcj2 and tcj4 contain C-terminal CaaX m otifs, substrates for prenyl modifications, suggesting that they are a ssociated with cellular membranes. tcj1 is a divergent member of the f amily, containing neither glycine/phenylalanine-rich nor zinc linger d omains. All the T. cruzi DnaJ genes are single copy, in contrast to ot her T. cruzi heat shock genes, which are arranged in multicopy direct tandem arrays. Among the tcj mRNAs, only tcj2 is heat inducible, which may result from posttranscriptional regulation involving a sequence f ound in the 3' untranslated regions of all heat-inducible T. cruzi mRN As described to date. Further study of this important family of protei n chaperones will aid our understanding of the protein folding and ass embly processes in protozoans. (C) 1998 Published by Elsevier Science B.V. All rights reserved.