title: A proline-rich structural protein of the surface sheath of larval Brugia filarial nematode parasites.
abstract: Both cDNA and genomic DNA sequences have been isolated which encode a proline-rich precursor protein of the sheath from microfilariae, the first stage larvae of the filarial nematode parasites Brugia pahangi and Brugia malayi. This 22-kDa protein is soluble only under reducing conditions and is extensively cross-linked by both disulfide and nonreducible bonds. Immunogold electron microscopy shows that the protein is localized exclusively in the sheath, a vestigial remnant of the eggshell, which is retained by and encloses the mature microfilaria. Analysis by Western blotting confirms that the protein is expressed only in microfilariae and adult female worms, although transcripts are detectable only in adult females. The deduced amino acid sequence contains a short N-terminal hydrophobic putative leader sequence, a central repetitive domain that contains 14 copies of a degenerate 5-amino acid repeat with the consensus sequence Met-Pro-Pro-Gln-Gly, and a C-terminal proline-rich domain flanked by clusters of cysteine residues. These clusters can be aligned with cysteine residues implicated in cross-linking of a family of cuticular collagens originally identified in Caenorhabditis elegans but which extends to other nematodes.
authors.affiliation: Wellcome Research Centre for Parasitic Infections, Department of Biochemistry, Imperial College of Science, Technology and Medicine, London, United Kingdom.
authors.forename: M E
authors.initials: ME
authors.lastname: Selkirk
authors.forename: M
authors.initials: M
authors.lastname: Yazdanbakhsh
authors.forename: D
authors.initials: D
authors.lastname: Freedman
authors.forename: M L
authors.initials: ML
authors.lastname: Blaxter
authors.forename: E
authors.initials: E
authors.lastname: Cookson
authors.forename: R E
authors.initials: RE
authors.lastname: Jenkins
authors.forename: S A
authors.initials: SA
authors.lastname: Williams
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D002009:Brugia / Q000235:genetics / Q000254:growth & development / Q000502:physiology* / Q000648:ultrastructure; D003545:Cysteine; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D015801:Helminth Proteins / Q000235:genetics* / Q000302:isolation & purification; D007814:Larva; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011498:Protein Precursors / Q000235:genetics* / Q000302:isolation & purification; D021382:Protein Sorting Signals / Q000235:genetics; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012091:Repetitive Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid
chemical_list: D015801:Helminth Proteins; D011498:Protein Precursors; D021382:Protein Sorting Signals; C069140:MF22 protein, Brugia pahangi; D012313:RNA; D003545:Cysteine