Skip to search boxSkip to navigationSkip to main content

The polyprotein and FAR lipid binding proteins of nematodes: shape and monomer/dimer states in ligand-free and bound forms

  • Lindsay McDermott
    ,
  • Alexandra S. Solovyova
    ,
  • Nicola Meenan
    ,
  • Antonio Garofalo
    ,
  • Jannette E. Bradley
    ,
  • Malcolm W. Kennedy
Research Output: Contribution to journal Article Peer-review

Abstract

Nematodes produce two classes of small, helix-rich fatty acid- and retinol-binding proteins whose structures and in vivo functions remain to be elucidated. These are the polyprotein allergens (NPA) and the FAR proteins. The solution properties of recombinant forms of these proteins from parasitic [Ascaris suum (As) and Onchocerca volvulus (Ov)] and free-living [Caenorhabditis elegans (Ce)] nematodes have been examined. Analytical ultracentrifugation (AUC) showed that, contrary to previous findings, the rAs-NPA-1A polyprotein unit (approximately 15 kDa) is a monomer, and this stoichiometry is unaltered by ligand (oleic acid) binding. The rOv-FAR-1 and rCe-FAR-5 proteins differ in that the former forms a tight dimer and the latter a monomer, and these oligomeric states are also unaffected by ligand binding or protein concentration. Sedimentation equilibrium experiments showed that the partial specific volume v of the unliganded proteins agree well with the value calculated from amino acid composition extrapolated to experimental temperature, and was unaffected upon ligand binding. Data from small-angle X-ray scattering (SAXS) indicated that both of the monomeric proteins rAs-NPA-1A and rCe-FAR-5 are globular, although slightly elongated and flattened. These data are in good agreement with shapes predicted from sedimentation velocity experiments and hydrodynamic bead modelling. On the basis of functional and secondary structural homology with the ligand-binding domain of the retinoic acid receptor RXRalpha, de novo atomic resolution structures for rAs-NPA-1A and rCe-FAR-5 have been constructed which are consistent with the SAXS and hydrodynamic data.

Publication Information

Output type

Research Output: Contribution to journal Article Peer-review

Original language

English

Pages from-to (Number of pages)

Pages 465-476

Journal (Volume, Issue Number)

European Biophysics Journal (Volume 32, Issue 5)

Publication milestones

  • Published - 31/08/2003

Publication status

Published - 31/08/2003

ISSN

0175-7571

External Publication IDs

  • handle.net: 10547/622677
  • Scopus: 0041857977

Access to documents

Publication metrics