A cathepsin L-like cysteine proteinase gene from the protozoan parasite, Cryptobia salmositica.

The present study describes the identification of a cathepsin L-like cysteine proteinase gene (CYS) from the hemoflagellate Cryptobia salmositica. Genomic DNA sequence of cysteine proteinase was obtained by genome walking using degenerate primers. Specific primers were designed to amplify the cDNA of cysteine proteinase from mRNA by rapid amplification of cDNA ends-PCR. The open reading frame of CYS is 1,329 bp, with 443 deduced amino acids. Based on the sequence analysis, cysteine proteinase of C. salmositica is similar to the cathepsin L-like cysteine proteinase of kinetoplastid parasites such as Leishmania spp. and Trypanosoma spp. The identification of CYS proteinase gene could help to design cysteine proteinase specific inhibitors. Further studies are required to characterize the complete genomic organization of the cysteine proteinase.