Cloning and expression in Escherichia coli of a Fasciola hepatica gene encoding a calcium-binding protein

A Fasciola hepatica cDNA clone of 994 bp was isolated from an adult worm cD NA expression library using a rabbit serum against the excretory-secretory antigens. The nucleotide sequence of the cDNA clone revealed the presence o f an open reading frame of 572 bp which encoded a 22 kDa polypeptide (Fh22) showing putative EF-hand domains. This gene was expressed in Escherichia c oli and the recombinant protein used for the production of specific antibod ies. Immunoblotting studies using the anti-Fh22 serum showed the presence o f a polypeptide of similar molecular mass in the excretory-secretory extrac t of the adult parasite. The recombinant Fh22 polypeptide showed calcium-de pendent electrophoretic mobility (decreased with Ca2+-ions and increased wi th EGTA). The observed behaviour of recombinant Fh22 in gel filtration expe riments also suggested calcium-induced conformational changes. (C) 1999 Pub lished by Elsevier Science B.V. All rights reserved.