A surface-associated retinol- and fatty acid-binding protein (Gp-FAR-1) from the potato cyst nematode Globodera pallida: lipid binding activities, structural analysis and expression pattern
A. Prior et al., A surface-associated retinol- and fatty acid-binding protein (Gp-FAR-1) from the potato cyst nematode Globodera pallida: lipid binding activities, structural analysis and expression pattern, BIOCHEM J, 356, 2001, pp. 387-394
Parasitic nematodes produce at least two structurally novel classes of smal
l helix-rich retinol- and fatty-acid-binding proteins that have no counterp
arts in their plant or animal hosts and thus represent potential targets fo
r new nematicides. Here we describe a protein (Gp-FAR-1) from the plant-par
asitic nematode Globodera pallida, which is a member of the nematode-specif
ic fatty-acid- and retinol-binding (FAR) family of proteins but localizes t
o the surface of this species, placing it in a strategic position for inter
action with the host. Recombinant Gp-FAR-1 was found to bind retinol, cis-p
arinaric acid and the fluorophore-tagged lipids 11-(dansylamino)undecanoic
acid and dansyl-D,L-alpha -amino-octanoic acid. The fluorescence emission c
haracteristics of the dansylated analogues indicated that the entire ligand
enters the binding cavity. Fluorescence competition experiments showed tha
t Gp-FAR-1 binds fatty acids in the range C-11 to C-24, with optimal bindin
g at C-15. Intrinsic fluorescence analysis of a mutant protein into which a
tryptophan residue had been inserted supported computer-based predictions
of the position of this residue at the protein's interior and possibly also
at the binding site. Of direct relevance to plant defence systems was the
observation that Gp-FAR-1 binds two lipids (linolenic and linoleic acids) t
hat are precursors of plant defence compounds and the jasmonic acid signall
ing pathway. Moreover, Gp-FAR-1 was found to inhibit the lipoxygenase-media
ted modification of these substrates in vitro. Thus not only does Gp-FAR-1
function as a broad-spectrum retinol- and fatty-acid-binding protein, the r
esults are consistent with the idea that Gp-FAR-1 is involved in the evasio
n of primary host plant defence systems.