Molecular characterization of a partial sequence encoding a novel Schistosoma mansoni serine protease.
A PCR strategy using degenerate oligonucleotide primers based upon consensus sequences of the active site of serine proteases yielded a 467 bp fragment from genomic DNA from Schistosoma mansoni cercariae. The sequence presented a continuous open reading frame and the deduced amino acid sequence (156 aa) presented homologies with various serine proteases, in particular the highest percentage identity was observed with a mammalian plasma kallikrein. The expression of this serine protease was studied first at the mRNA level and it was only detected by RT-PCR in cercariae and in adult worms. At the protein level we were able to detect it by Western blotting and by using antigen extracts from metabolically radio-isotope labelled worms. The absence of any positive signal in Northern blot and the detection of the protein suggest that the mRNA has a very short half-life, however the protein may be accumulated in the parasite. The significance of identity with mammalian kallikrein was confirmed by cross-immunoreactivity with a native porcine pancreatic kallikrein. However, no cross-reactivity was observed with S. mansoni elastase, another serine protease. Thus, we suggest that the serine protease described in this paper is a kallikrein-like protease.
Cocude
C
C
Centre d'Immunologie et de Biologie Parasitaire, INSERM U167, Institut Pasteur, Lille, France. Cecile.Cocude@pasteur-lille.fr
Pierrot
C
C
Cetre
C
C
Godin
C
C
Capron
A
A
Khalife
J
J
D000595:Amino Acid Sequence; D000818:Animals; D000909:Antibodies, Helminth; D001483:Base Sequence; D003001:Cloning, Molecular; D015801:Helminth Proteins / Q000235:genetics*; D015151:Immunoblotting; D007610:Kallikreins / Q000235:genetics; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011233:Precipitin Tests; D018510:RNA, Helminth / Q000302:isolation & purification; D012333:RNA, Messenger / Q000302:isolation & purification; D012550:Schistosoma mansoni / Q000201:enzymology / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000235:genetics* / Q000276:immunology
D000909:Antibodies, Helminth; D015801:Helminth Proteins; D018510:RNA, Helminth; D012333:RNA, Messenger; D007610:Kallikreins; D012697:Serine Endopeptidases