Brugia pahangi and Brugia malayi: A Surface-Associated Glycoprotein (gp15/400) Is Composed of Multiple Tandemly Repeated Units and Processed from a 400-kDa Precursor

Abstract

The cuticle of filarial nematode parasites contains distinct and separable sets of soluble and structural proteins. Surface-labeling techniques have previously identified a soluble protein complex in adult stage Brugia which ranges in molecular weight from 15 to 200 kDa. Using an antiserum directed to the 15-kDa basal subunit of this complex, we show here that this complex is synthesized and processed from a single, very large precursor protein with a molecular weight of approximately 400 kDa. Molecular cloning, sequencing, and Southern analysis indicates that the protein is encoded by a single gene composed predominantly of approximately 20 tandemly repeated segments of 396 bp. The two complete copies of these repeated segments in our cDNA sequence are identical. Each subunit of 132 amino acids bears a consensus site for N-linked glycosylation, and glycosidase treatment indicates that this corresponds to an oligosaccharide side chain of 2 kDa. The protein displays no significant homology to sequences lodged in databases corresponding to molecules of known function. Nevertheless, a significant similarity (19/41 residues) is observed with the N-terminal sequence of a protein termed ABA-1, an allergen from Ascaris.