Structural characterization of a putative fatty acid binding-domain from Leishmania amazonensis

Leishmania parasites rely on host-derived lipids and fatty acids (FAs) to support membrane biogenesis, metabolic adaptation, and proliferation. However, the intracellular mechanisms that coordinate FA trafficking in these parasites remain poorly understood.  Fatty acid-binding proteins (FABPs) function as lipid chaperones in eukaryotes. No FABP-like protein has been characterized in trypanosomatids. Here we identified LFABP1 (Leishmania fatty acid-binding protein 1), a conserved hypothetical protein containing a C-terminal FABP-like domain that is conserved throughout the genus Leishmania and has putative orthologs in Trypanosoma cruzi. The Leishmania amazonensis LFABP1 C-terminal domain was expressed as a recombinant protein, purified and crystallized. The crystal structure obtained at 1.57 Å reveals a unique FABP fold, displaying additional N-terminal α-helices and a third α-helix within the conserved helix-loop-helix motif. An anti-LFABP1^CTDpolyclonal antiserum detected endogenous LFABP1 in protein extracts from both promastigote and amastigote stages of L. amazonensis. Together, these findings establish LFABP1 as the first characterized FABP-like domain in Leishmania. This domain was fused to an AttH-like domain along the evolutionary history, and this multi-domain architecture is found only in kinetoplastids.