Parasitic nematodes have recently been found to produce proteins which repr
esent two new classes of fatty acid and retinoid binding protein. The first
is the nematode polyprotein allergens/antigens (NPAs) which, as their name
suggests, are synthesised as large polyproteins which are subsequently cle
aved at regularly spaced sites to form multiple copies of a fatty acid bind
ing protein of approximately 14.5 kDa. Binding studies using molecular envi
ronment-sensitive fluorescent ligands have shown that the binding site is h
ighly unusual, producing blue-shifting in fluorescence to an unprecedented
degree, suggesting a remarkably non-polar environment and isolation from so
lvent water. Computer-based structural predictions and biophysical observat
ions have identified the NPAs as highly helical proteins which might form a
four helix bundle, so constitute a new class of lipid binding protein from
animals. The second class, like the NPAs, binds both fatty acids and retin
ol, but with a higher affinity for the latter. These are also highly helica
l but are structurally distinct from the NPAs. The biological function of t
hese new classes of protein are discussed in the context of both the metabo
lic requirements of the parasites and the possible role of the proteins in
control of the immune and inflammatory environment of the tissue sites para
sitised.