1H, 13C and 15N chemical shift assignments of Na-FAR-1, a helix-rich fatty acid and retinol binding protein of the parasitic nematode Necator americanus

The fatty acid and retinol-binding (FAR) proteins are a family of unusual helix-rich lipid binding proteins found exclusively in nematodes, and are secreted by a range of parasites of humans, animals and plants. Na-FAR-1 is from the parasitic nematode Necator americanus, an intestinal blood-feeding parasite of humans. Sequence-specific (1)H, (13)C and (15)N resonance assignments have been obtained for the recombinant 170 amino acid protein, using three-dimensional triple-resonance heteronuclear magnetic resonance experiments. Backbone assignments have been obtained for 99.3% of the non-proline HN/N pairs (146 out of 147). The amide resonance of T45 was not observed, probably due to rapid exchange with solvent water. A total of 96.9% of backbone resonances were identified, while 97.7% assignment of amino acid sidechain protons is complete. All Hα(166), Hβ(250) and Hγ(160) and 98.4% of the Hδ (126 out of 128) atoms were assigned. In addition, 99.4% Cα (154 out of 155) and 99.3% Cβ (143 out of 144) resonances have been assigned. No resonances were observed for the NH(n) groups of R93 NεHε, arginine, N(η1)H2, N(η2)H2, histidine N(δ1)H(δ1), N(ε1)H(ε1) and lysine N(ζ3)H3. Na-FAR-1 has a similar overall arrangement of α-helices to Ce-FAR-7 of the free-living Caeorhabditis elegans, but with an extra C-terminal helix.