Characterization and phylogenetic analysis of a mitochondrial targeting alpha/beta hydrolase protein in Strongyloides ratti

Strongyloides ratti is widely used as an experimental model for studying and diagnosing humans strongyloidiasis. The alpha/beta hydrolase domain proteins are ubiquitously distributed across all organisms. In this study, a 780-nucleotide cDNA fragment was amplified by RT-PCR, and BLAST analysis revealed that 98.54% sequence identity with the only incomplete S. ratti mRNA sequence available in GenBank (XM_024652394.1). Using this fragment as a probe, two expressed sequence tags (ESTs), 856 bp (FC815910.1) and 526 bp (BI742498.1), corresponding to the 3'and 5' ends, respectively, were identified and assembled into a full length cDNA of 919 bp, designated SrABH. Its amino acid sequence exhibited 97.98% identity with the only available S. ratti sequence in GenBank (XP_024505975.1). The molecular weight (MW) and isoelectric point (pI) of the protein are 33.484 kDa and 7.18, respectively. Signal peptide analysis indicated the absence of a secretion signal, however a mitochondrial targeting cleavage site was identified between amino acids 21-22. The highly conserved motif consists of nine amino acids spanning positions 111 to 120. The 3D structural analysis revealed that SrABH consists of 9 alpha-helices (39.18%), 8 beta-sheets (18.21%), and loop regions (42.61%). Phylogenetic analysis clustered SrABH with related nematode sequences, displaying by a high bootstrap support of 98. The lowest genetic distance (0.01%) was observed between SrABH and the only sequence isolated from S. ratti (XP_024505975.1). Given its molecular characteristics, this parasite’s data may be valuable in structure-based drug design strategies using S. ratti as a model system for the human pathogen S. stercoralis.