Schistosoma mansoni: SmLIMPETin, a member of a novel family of invertebrate-only regulatory proteins.

Eukaryotic LIM domain proteins contain zinc finger forming motifs rich in cysteine and histidine that enable them to interact with other proteins. A cDNA clone isolated from an adult schistosome cDNA library revealed a sequence that coded for a novel class of proteins bearing 6 LIM domains and an N-terminal PET domain, SmLIMPETin. Phylogeny reconstruction of SmLIMPETin and comparison of its sequence to invertebrate homologues and to the vertebrate four-and-a-half LIM domains protein family (FHLs), uncovered a novel LIM domain protein family, the invertebrate LIM and PET domain protein family (LIMPETin).

The N-terminus moiety of the cystatin SmCys from Schistosoma mansoni regulates its inhibitory activity in vitro and in vivo.

The complete sequence of SmCys, a cystatin expressed by Schistosoma mansoni, was obtained. Constructs of SmCys consisting of deletions of 10 and 20 amino acid residues from the N-terminal of the full length recombinant protein, were cloned in the pQE-30 vector, expressed in Escherichia coli and assayed for inhibitory activity against papain. Kinetic analysis showed that SmCys -10 and SmCys -20 had K(i) values of 0.