Exploring structural features of a potential fatty acid binding protein of Leishmania amazonensis

Lipids and fatty acids are essential nutrients that trypanosomatid parasites acquire from their hosts for survival.These nutrients are essential in specific stages of the Leishmania life cycle, significantly influencing differentiation, modulation of the host immune response, and susceptibility to therapeutic agents. However, the mechanisms by which Leishmania spp. acquire and process lipids remain poorly understood. Fatty acid-binding proteins (FABPs) are essential lipid chaperones that facilitate the intracellular transport of lipids. Bioinformatic analysis of Leishmania genomes identified lfabp1, which encodes a protein previously annotated as "hypothetical" but predicted to have structural similarities to eukaryotic FABPs. In this study, lfabp1 expression was confirmed in L. amazonensis through qPCR and western blot analyses. Employing CRISPR-Cas9 we generated parasite strains expressing LFABP1-mNeoGreen. Fluorescence microscopy assays suggested that LFABP1 is predominantly located in the nucleus. The LFABP1 C-terminal domain (LeiFABP) was crystallized using the sitting drop method, and X-ray diffraction data were collected at the synchrotron beamline Manacá (Sirius/CNPEM). The structure at 1.8Å resolution confirmed that LeiFABP displays a FABP-like folding, consisting of ten antiparallel beta-strands forming a barrel and a helix-loop-helix motif. LeiFABP displays extensive homology with other FABPs, including Sm14 from Schistosoma mansoni and EgFABP1 from Echinococcus granulosus, and conserves key residues involved in arachidonic acid binding.  Altogether these results suggest that LFABP1 could be a key component in lipid metabolism and cell response related to the parasite's lipid biology. Supported by Fapesp (Process: 2023/02831-9).