CLONING AND EXPRESSION OF A CDNA-ENCODING A NONINTEGRIN LAMININ-BINDING PROTEIN FROM ECHINOCOCCUS-GRANULOSUS WITH LOCALIZATION OF THE LAMININ-BINDING DOMAIN

We have isolated a cDNA from the hydatid tapeworm, Echinococcus granul osus, encoding a protein that binds laminin. This is the first report of a helminth parasite laminin-binding protein and the first descripti on of a cDNA encoding a laminin-binding protein from a parasite. The c DNA clone (egmo3) was isolated from an E. granulosus protoscolex cDNA expression library, and identified on the basis of sequence homology t o the nonintegrin mammalian metastasis-associated 67-kDa laminin recep tor (67-LR). The amino acid sequence predicted from the cDNA sequence is 268 residues long with a calculated molecular mass of 29.9 kDa. Sou thern blot analysis suggested that many copies of the gene may occur i n the E. granulosus genome. A Northern blot revealed that the gene is expressed as a single transcript of approximately 1 kb consistent with the size of the cDNA insert. Antibodies raised to the purified protei n interacted with a 30 kDa protein in whole E. granulosus protoscolece s. A Western blot of the purified and refolded recombinant protein spe cifically bound I-125-labelled laminin, as did a synthetic peptide der ived from the inferred amino acid sequence of egmo3 which is similar i n homology to peptide G, the active ligand-binding site of 67-LR. We a lso isolated the 3' end of the cDNA encoding the homologous protein fr om the closely related species, E. multilocularis. The polypeptide enc oded by egmo3 also shares substantial identity with the acidic class o f ribosomal proteins which are involved in protein synthesis. As such, the egmo3 protein may be multifunctional in E. granulosus, acting as a laminin-binding molecule but also playing a role in cell division an d growth. (C) 1997 Elsevier Science B.V.