To study the interactions between the paraprotozoan Giardia lamblia and its environment, we have d he gene that encodes the two major surface-labeled hozoite protein species. Sequence analysis of this gene ls a single open reading frame specifying a hydrophilic, ine-rich (11.8%) protein of 72.5-kDa molecular mass with mino-terminal signal peptide and a postulated hydrophobic brane-spanning anchor region near the carboxyl termis. Most of the cysteine residues (58 of 84) are in the motif s-Xaa-Xaa-Cys, which is dispersed 29 times throughout the ence. Antibodies against the recombinant protein react the entire surface of live trophozoites, including flagella adhesive disc. These antibodies inhibit trophozoite attacht, prevent growth, and immunoprecipitate the major ≈66-d 85-kDa proteins from surface-labeled live trophozoites. recombinant Escherichia coli also expresses polypeptides ≈66- and 85-kDa molecular mass, which are not fusion teins. This suggests that the processing and/or conformaal changes that lead to production of these two peptide cies in E. coli reflect those that occur in Giardia. The endance of cysteine residues suggests that the native proteins the parasite surface may contain numerous disulfide bonds, ich would promote resistance to intestinal fluid proteases to the detergent activity of bile salts and would help to lain the survival of Giardia in the human small intestine.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|Publication status||Published - 1990|
- Protozoan parasite
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