Isolation and expression of the gene for a major surface protein of Giardia lamblia

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 87; no. 12; pp. 4463 - 4467
• Main Authors: Gillin, F.D. (University of California, San Diego, CA), Hagblom, P, Harwood, J, Aley, S.B, Reiner, D.S, McCaffery, M, So, M, Guiney, D.G
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01.06.1990; National Acad Sciences
• Subjects: ACIDE AMINE; ADN; Amino Acid Sequence; AMINO ACIDS; AMINOACIDOS; Animals; Antibodies; Antibodies, Protozoan; Antigen-Antibody Complex; ANTIGENE; ANTIGENOS; ANTIGENS; Antigens, Protozoan - genetics; Antiserum; Base Sequence; Biological and medical sciences; Cell membranes; DNA; DNA - genetics; ESCHERICHIA; ESCHERICHIA COLI; Flagella; Fundamental and applied biological sciences. Psychology; GENE; Gene expression; GENES; GENOMAS; GENOME; GENOMES; Genomic Library; Giardia - genetics; Giardia - immunology; INFECCIONES POR PROTOZOARIOS; MASTIGOPHORA; Membrane Proteins - genetics; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; NUCLEOTIDE; NUCLEOTIDES; NUCLEOTIDOS; Parasites; PROTEINAS; PROTEINE; PROTEINS; PROTOZOAL INFECTIONS; PROTOZOOSE; Trophozoites; Protozoa; Cell culture; Host parasite relation; Cysteine; Nucleotide sequence; Gene expression; Antigen; Proteins; Trophozoite; Gene; Giardia intestinalis; Rhizoflagellata; Immunoelectron microscopy; Immunofluorescence; Aminoacid sequence
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.87.12.4463

To study the interactions between the parasitic protozoan Giardia lamblia and its environment, we have cloned the gene that encodes the two major surface-labeled trophozoite protein species. Sequence analysis of this gene reveals a single open reading frame specifying a hydrophilic, cysteine-rich (11.8%) protein of 72.5-kDa molecular mass with an amino-terminal signal peptide and a postulated hydrophobic membrane-spanning anchor region near the carboxyl terminus. Most of the cysteine residues (58 of 84) are in the motif Cys-Xaa-Xaa-Cys, which is dispersed 29 times throughout the sequence. Antibodies against the recombinant protein react with the entire surface of live trophozoites, including flagella and adhesive disc. These antibodies inhibit trophozoite attachment, prevent growth, and immunoprecipitate the major ≈ 66- and 85-kDa proteins from surface-labeled live trophozoites. The recombinant Escherichia coli also expresses polypeptides of ≈ 66- and 85-kDa molecular mass, which are not fusion proteins. This suggests that the processing and/or conformational changes that lead to production of these two peptide species in E. coli reflect those that occur in Giardia. The abundance of cysteine residues suggests that the native proteins on the parasite surface may contain numerous disulfide bonds, which would promote resistance to intestinal fluid proteases and to the detergent activity of bile salts and would help to explain the survival of Giardia in the human small intestine.