Giardia fibrillarin: a bioinformatics exploration of sequence and structure

Fibrillarin is a key nucleolar S-adenosyl-L-methionine (SAM)-dependent methyltransferase, highly conserved among species in both sequence and function. It is actively involved in numerous cellular processes, particularly in the early stages of pre-ribosomal RNA processing. Although a fibrillarin orthologue has been identified in Giardia, an intestinal protozoan parasite responsible for numerous infections worldwide, its functional and structural features in this parasite remain largely unexplored. In this study, bioinformatics tools were used to analyze the sequence and structure of Giardia fibrillarin to provide insights that could aid future experimental and therapeutic investigations. Taking advantage of the protein sequence of Giardia fibrillarin, multiple bioinformatics tools were employed to estimate its domains, nuclear and nucleolar localization signals (NLS and NoLS), post-translational modifications, phylogeny, and three-dimensional structure. The analysis revealed significant conservation of Giardia fibrillarin, showing close relationships with archaeal and parasitic amoeba orthologs. It retains essential features such as the SAM-dependent methyltransferase domain, a glycine- and arginine-rich domain, and both NLS and NoLS. While the core region of the protein is structurally conserved, the N-terminal region exhibits notable divergence. The potential for inhibition of Giardia fibrillarin by SAM competitors suggests that it could be a promising target for drug development, particularly for strains resistant to current treatments.