Molecular Characterization of the cDNA Coding for Translation Elongation Factor-2 of PathogenicEntamoeba histolytica

Abstract

To investigate the humoral immune response of patients with amoebic dysentry against Entamoeba histolytica, immunoglobulin G (IgG)-immunopositive cDNA clones from the pathogenic strain SFL-3 were examined. A large part of the IgG-positive cDNA clones obtained with one serum encoded highly conserved intracellular proteins. A clone was found that was homologous to translation elongation factor-2 (EF-2). Sequence analysis of the EF-2 cDNA showed 63.6% amino acid sequence identity with the human homologue. The deduced protein sequence has a length of 840 amino acid residues with a molecular mass of 93.3 kD. The 3' and 5' untranslated regions of the mRNA are relatively short as shown for other genes of E. histolytica. A genomic clone was used to analyze the region upstream of the translation initiation codon. The codon distribution of EF-2 and other published E. histolytica sequences reflects the high A/T content. The codons for different amino acids are biased to a widely differing extent.