Structural highlights
Publication Abstract from PubMedIntracellular lipid binding proteins (iLBPs) of the FABP family of animals transport mainly fatty acids or retinoids, are confined to the cytosol, and have highly similar three-dimensional structures. In contrast, nematodes possess fatty acid binding proteins (nemFABPs) that are secreted into the perivitelline fluid surrounding their developing embryos. We report structures of As-p18, a nemFABP of the large intestinal roundworm Ascaris suum, with ligand bound, determined using X-ray crystallography and nuclear magnetic resonance spectroscopy. In common with other FABPs, As-p18 comprises a ten beta-strand barrel capped by two short alpha-helices, with the carboxylate head group of oleate tethered in the interior of the protein. However, As-p18 exhibits two distinctive longer loops between beta-strands not previously seen in a FABP. One of these is adjacent to the presumed ligand entry portal, so may help to target the protein for efficient loading or unloading of ligand. The second, larger loop is at the opposite end of the molecule and has no equivalent in any iLBP structure yet determined. As-p18 preferentially binds a single 18-carbon fatty acid ligand in its central cavity but in an orientation that differs from iLBPs. The unusual structural features of nemFABPs may relate to resourcing of developing embryos of nematodes. As-p18, an extracellular fatty acid binding protein of nematodes, exhibits unusual structural features.,Ibanez-Shimabukuro M, Rey-Burusco MF, Gabrielsen M, Franchini GR, Riboldi-Tunnicliffe A, Roe AJ, Griffiths K, Cooper A, Corsico B, Kennedy MW, Smith BO Biosci Rep. 2019 Jul 4. pii: BSR20191292. doi: 10.1042/BSR20191292. PMID:31273060[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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