Genomic Cloning and Sequence Analysis of Trypanosoma brucei rhodesiense Gene Encoding Putative N-glycosylation Enzyme
Baticados, Waren NavarraInoue, NoboruSugimoto, ChihiroNagasawa, HideyukiBaticados, Abigail Morales
Background: Trypanosoma brucei rhodesiense is a haemoflagellate parasite of zoonotic significance. Aside from its public health importance, this parasite subspecies gained notoriety because of their effective system to circumvent the immune response of vertebrate host. The parasite cell surface is covered with millions of VSG dimers, which serve as an almost infinite repertoire of biomolecules needed for evasion of host immune system. Around two decades ago, it was resolved that all trypanosome VSG is associated with one or more N-linked oligosaccharides, with a range of structures including high mannose and complex types. This complex process of protein modification known as N-linked glycosylation is catalyzed by oligosaccharyl transferase (OST). In general, the incorporation of glycan structures can alter proteins antigenic properties and recently it was established that glycan molecules associated with VSG were found to be important in several aspects of trypanosome-host interaction, especially during parasite evasion of the host defense mechanisms. Therefore, our major interest is to clone and characterize the trypanosome OST. Materials, Methods & Results: The template genomic DNA for PCR amplification was extracted as described previously. In an attempt to clone Trypanosoma brucei rhodesiense putative oligosaccharyl transferase, an amplicon of ~2000 bp was obtained having an open reading frame of 2057 bp and deduced primary structure composed of 685 amino acid residues (TbrOST II). Comparison of TbrOST II ORF with annotated putative oligosaccharyl transferase in the genome of other organisms revealed sequence identity to other kinetoplastid. TbrOST II had high nucleotide (Ns) and amino acid (As) sequence similarity with the genomes of T. brucei gambiense (Ns:99%; As:78%) and T. brucei (Ns:95-98%; As:77%-98%). There was also significant nucleotide and(...)
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