Secretion of a Novel, Developmentally Regulated Fatty Acid-Binding Protein Into the Perivitelline Fluid of the Parasitic Nematode, Ascaris Suum

B Mei, M W Kennedy, J Beauchamp, P R Komuniecki, R Komuniecki

J Biol Chem. 1997 Apr 11;272(15):9933-41.

PMID: 9092532

Abstract:

Early development of the parasitic nematode, Ascaris suum, occurs inside a highly resistant eggshell, and the developing larva is bathed in perivitelline fluid. Two-dimensional gel analysis of perivitelline fluid from infective larvae reveals seven major proteins; a cDNA encoding one of these, As-p18, has been cloned, sequenced, and protein expressed in Escherichia coli. The predicted amino acid sequence of As-p18 exhibits similarities to the intracellular lipid-binding protein (iLBP) family including retinoid- and fatty acid-binding proteins (FABP). As-p18 is unusual in that it possesses a hydrophobic leader that is not present in the mature protein, the developmental regulation of its expression, and in terms of its predicted structure. Recombinant As-p18 is a functional FABP with a high affinity for both a fluorescent fatty acid analog (11(((5-(dimethylamino)-1-naphthalenyl)sulfonyl)amino) undecanoic acid) and oleic acid, but not retinol. Circular dichroism of rAs-p18 reveals a high beta-sheet content (62%), which is consistent with secondary structure for the protein predicted from sequence algorithms, and the structure of iLBPs. Unusual features are apparent in a structural model of As-p18 generated from existing crystal structures of iLBPs. As-p18 is not found in unembryonated eggs, begins to be synthesized at about day 3 of development, reaches a maximal concentration with the formation of the first-stage larva and remains abundant in the perivitelline fluid of the second-stage larva. Since As-p18 is not present in the post-infective third-stage larva or adult worm tissues, it appears to be exclusive to the egg. Surprisingly, however, Northern blot analysis yields mRNA for As-p18 not only in the early larval stages, but also the unembryonated egg, third-stage larvae, and ovaries of adult worms, even though the protein is not detectable from any of those sources. As-p18 may play a role in sequestering potentially toxic fatty acids and their peroxidation products, or it may be involved in the maintenance of the impermeable lipid layer of the eggshell.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP73025022	11-[5-(Dimethylamino)-1-naphthalenesulfonylamino]undecanoic acid		73025-02-2	Price