A head-to-tail tandem organization of hsp70 genes inTrypanosoma cruzi

We describe the isolation and characterization of the T. cruzi hsp 7DNA coding region which wss found to be formed by multigene copies organized in a tande$$$ array in a bead-to-tail manner. The restriction pattern of one of the repetition units whithin the largest clone obtained from the genomic library, clone Tc70.6, shows that the hsp70 coding region should be formed by at least seven identical copies of 2.5 Kb. We have found, however, the presence of restriction polimorphis$$$s (Pvu II) within these repeats. Subsequent analysis of the time course of nuclear DNA digestion has revealed that the copy number per haploid geno$$$e could be as greater as 10. The analysis of the DNA and amino acid sequence of a fragment (70%) of one of the repetition units has shown the existance of a high homology with all the hsp70 genes of other organisms. The protein sequence homology of the fragment analyzed is as high as 88% when compared with that of the T. brucei hsp70. On the other hand, there are significant restriction site variations between both. The T. cruzi hsp70 contains at the C-terminal end a tetrapeptide repeat of the structure (G$$$PG)₉.