Solution structure of As-p18 reveals that nematode fatty acid binding proteins exhibit unusual structural features

Experimental Data Snapshot

  • Method: SOLUTION NMR
  • Conformers Calculated: 100 
  • Conformers Submitted: 20 
  • Selection Criteria: structures with the lowest energy 

wwPDB Validation   3D Report Full Report

This is version 1.2 of the entry. See complete history


As-p18, an extracellular fatty acid binding protein of nematodes, exhibits unusual structural features.

Ibanez-Shimabukuro, M.Rey-Burusco, M.F.Gabrielsen, M.Franchini, G.R.Riboldi-Tunnicliffe, A.Roe, A.J.Griffiths, K.Cooper, A.Corsico, B.Kennedy, M.W.Smith, B.O.

(2019) Biosci Rep 

  • DOI: https://doi.org/10.1042/BSR20191292
  • Primary Citation of Related Structures:  
    6I8X, 6I9F

  • PubMed Abstract: 

    Intracellular lipid-binding proteins (iLBPs) of the fatty acid-binding protein (FABP) family of animals transport, mainly fatty acids or retinoids, are confined to the cytosol and have highly similar 3D 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 β-strand barrel capped by two short α-helices, with the carboxylate head group of oleate tethered in the interior of the protein. However, As-p18 exhibits two distinctive longer loops amongst β-strands not previously seen in a FABP. One of these is adjacent to the presumed ligand entry portal, so it 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.

  • Organizational Affiliation

    Instituto de Investigaciones Bioquímicas de La Plata, CONICET-UNLP, Facultad de Ciencias Médicas, calles 60 y 120, 1900-La Plata, Argentina.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Fatty acid-binding protein homolog155Ascaris suumMutation(s): 0 
Find proteins for P55776 (Ascaris suum)
Explore P55776 
Go to UniProtKB:  P55776
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP55776
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 1 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
OLA (Subject of Investigation/LOI)
Query on OLA

Download Ideal Coordinates CCD File 
C18 H34 O2
Experimental Data & Validation

Experimental Data

  • Method: SOLUTION NMR
  • Conformers Calculated: 100 
  • Conformers Submitted: 20 
  • Selection Criteria: structures with the lowest energy 

Structure Validation

View Full Validation Report

Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
Wellcome TrustUnited Kingdom083625

Revision History  (Full details and data files)

  • Version 1.0: 2019-07-17
    Type: Initial release
  • Version 1.1: 2023-06-14
    Changes: Data collection, Database references, Other
  • Version 1.2: 2024-06-19
    Changes: Data collection, Database references