Search

Background: This study characterizes two long vesicle-associated membrane protein (VAMP) genes (SYBL-1 and SYBL-2) obtained from DNA of Entamoeba histolytica by PCR amplification. (Nucleotide sequences of the Entamoeba histolytica SYBL-1 and SYBL-2 genes appear in the GeneBank under accession numbers AY256852 and AY309014.) Methods: The two cDNA products include one of 663 bp with sequence of 220 deduced amino acids, and a second of 693 bp with 230 deduced amino acid residues. Both products possess corresponding sequences for longin domain at N-terminus, a soluble N-ethylmaleimide-sensitive factor [NSF] attachment protein receptor (SNARE) coiled-coil region, a transmembrane domain (TM), and an intravesicular tail C-terminal, characteristics of all long VAMPs or longins. The current study identified presence of deduced peptide bonds in SYBL-1 and -2, which indicates that these two long VAMPs from E. histolytica could be appropriate substrates for zinc endopeptidases from tetanus and botulinum neurotoxins with specific activity toward neuronal synaptobrevins. Results: Alignment by Basic Local Alignment Search Tool (BLAST) of deduced amino-acid sequence of long VAMPs genes SYBL-1 and -2 showed identity of between 20 and 40% with Caenorhabditis elegans, Dictyostelium discoideum, Drosophila melanogaster, Arabidopsis thaliana, Mus musculus, Homo sapiens, and Plasmodium falciparum. Conclusions: It is possible that these two putative transport proteins are involved in endocytosis/exocytosis during a biological membrane fusion process, which may make them suitable candidates as targets for new drugs. According to published data, this is the first time that two such genes have been isolated from E. histolytica. [Copyright &y& Elsevier]

Abstract: This paper presents definitive data showing that the thiol-bimane compound isolated and purified by HPLC from Naegleria fowleri trophozoites unequivocally corresponds by matrix assisted laser-desorption ionization-time-of-flight MS, to the characteristic monoprotonated ion of trypanothione-(bimane)2 [M+H+] of m/z 1104.57 and to the trypanothione-(bimane) of m/z 914.46. The trypanothione disulfide T(S)2 was also found to have a molecular ion of m/z 723.37. Additionally HPLC demonstrated that thiol-bimane compounds corresponding to cysteine and glutathione were present in Naegleria. The ion patterns of the thiol-bimane compounds prepared from commercial trypanothione standard, Entamoeba histolytica and Crithidia luciliae are identical to the Naegleria thiol-bimane compound. Partially purified extracts from N. fowleri showed the coexistence of glutathione and trypanothione reductases activities. There is not doubt that the thiol compound trypanothione, which was previously thought to occur only in Kinetoplastida, is also present in the human pathogens E. histolytica and N. fowleri, as well as in the non-pathogenic euglenozoan E. gracilis. The presence of the trypanothione/trypanothione reductase system in N. fowleri creates the possibility of using this enzyme as a new “drug target” for rationally designed drugs to eliminate the parasite, without affecting the human host. [Copyright &y& Elsevier]

Background: Triatoma dimidiata is among the main vectors of Chagas disease in Latin America. However, and despite important advances, there is no consensus about the taxonomic status of phenotypically divergent T. dimidiata populations, which in most recent papers are regarded as subspecies. Methodology and Findings: A total of 126 cyt b sequences (621 bp long) were produced for specimens from across the species range. Forty-seven selected specimens representing the main cyt b clades observed (after a preliminary phylogenetic analysis) were also sequenced for an ND4 fragment (554 bp long) and concatenated with their respective cyt b sequences to produce a combined data set totalling 1175 bp/individual. Bayesian and Maximum-Likelihood phylogenetic analyses of both data sets (cyt b, and cyt b+ND4) disclosed four strongly divergent (all pairwise Kimura 2-parameter distances >0.08), monophyletic groups: Group I occurs from Southern Mexico through Central America into Colombia, with Ecuadorian specimens resembling Nicaraguan material; Group II includes samples from Western-Southwestern Mexico; Group III comprises specimens from the Yucatán peninsula; and Group IV consists of sylvatic samples from Belize. The closely-related, yet formally recognized species T. hegneri from the island of Cozumel falls within the divergence range of the T. dimidiata populations studied. Conclusions: We propose that Groups I–IV, as well as T. hegneri, should be regarded as separate species. In the Petén of Guatemala, representatives of Groups I, II, and III occur in sympatry; the absence of haplotypes with intermediate genetic distances, as shown by multimodal mismatch distribution plots, clearly indicates that reproductive barriers actively promote within-group cohesion. Some sylvatic specimens from Belize belong to a different species – likely the basal lineage of the T. dimidiata complex, originated ∼8.25 Mya. The evidence presented here strongly supports the proposition that T. dimidiata is a complex of five cryptic species (Groups I–IV plus T. hegneri) that play different roles as vectors of Chagas disease in the region. [ABSTRACT FROM AUTHOR]