Characterization of a Schistosoma mansoni gene encoding a homologue of the Y-box binding protein

We have cloned and characterized a Schistosoma mansoni cDNA encoding a basic protein homologous to the human Y-box binding protein 1 (YB-1). The 1.3-kb S. mansoni YB-1 transcript, which was shown to be expressed in various stages of the parasite life cycle, codes for a protein of 217 amino acids containing, towards its N-terminus, a nucleic acid binding motif, known as the cold-shock domain (CSD). This domain is 64% identical to the cold-shock domain of other members of the Y-box binding protein family and 43% identical to the cold-shock protein CspA of Escherichia coli. In S. mansoni YB-1, the cold-shock domain possess some structural characteristics that permit dimer formation as occurs in the Bacillus subtilis cold-shock protein CspB. The C-terminal region of S. mansoni YB-1 differs from the other Y-box binding proteins because of the presence of tandem repeats of Arg and Gly, suggesting the formation of a fibroin-like beta-sandwich structure. This novel folding pattern for the C-terminus of S. mansoni YB-1 might suggest a distinct specific function for this protein in the parasite.