A gene encoding a cysteine proteinase from Paragonimus westermani has been
cloned and expressed in Escherichia coli. The cysteine proteinase cDNA frag
ment was amplified by reverse transcription-polymerase chain reaction (RT-P
CR) using degenerate oligonucleotide primers derived from the conserved act
ive site of the cysteine proteinase. The 5' and 3' regions of the gene were
amplified using a PCR technique for the rapid amplification of cDNA ends.
The cloned gene has an open reading frame of 687 bp and deduced amino acid
sequence of 229. Sequence analysis and alignment showed significant homolog
ies with the eukaryotic cysteine proteinases and conservation of the Cys, H
is, and Asp residues that form a catalytic tried. Analysis of the expressed
protein on sodium dodecyl sulfate polyacrylamide gel electrophoresis showe
d that the molecular weight of the protein was approximately 28.5 kDa. The
expressed protein reacted with the sera of patients with paragonimiasis but
not with the sera of fascioliasis and clonorchiasis. These results suggest
that the expressed protein may be valuable as a specific diagnostic materi
al for the immunodiagnosis of paragonimiasis.