Molecular characterization of a partial sequence encoding a novel Schistosoma mansoni serine protease

Abstract

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.

Trypsin- and Chymotrypsin-Like Serine Proteases in Schistosoma mansoni – ‘The Undiscovered Country’

“…This number is significantly lower than the 135 family S1 proteases found in the human genome [8], [25] and may be due to the lack of need to regulate the more complex and expanded physiological processes found in vertebrates [55]. In our study and apart from SmSP1 [13], [14], we identified four additional SmSP genes encoding typical sequence features of the S1 family [7], [8] and which we term SmSP2 through SmSP5. Two further genes (Smp_194090 and Smp_06530 in GeneDB) were identified in the S. mansoni GeneDB as putative proteolytically inactive SmSPs as they lack the catalytic serine or histidine residue in the catalytic triad.…”

“…The five remaining SmSP genes, including the previously sequenced and partially characterized SmSP1 [13], [14], were cloned and sequenced. The other four gene sequences named SmSP2 through SmSP5 (Table 1) were significantly corrected and re-annotated in the primary database ( S. mansoni GeneDB) due to various sequence inaccuracies.…”

“…Both activities displayed trypsin type cleavage specificities and both may contribute to the phenomenon, whereby large occlusions of veins by schistosomes are not associated with intravascular deposition of fibrin and thrombus formation [52]–[54]. At the gene and primary sequence levels, however, only two SmSPs, namely SmSP1 [13], [14] and another [23], [24], which we term SmSP2, have been described.…”

“…Among these, SmSP1 ( S. mansoni serine protease 1, GenBank AJ011561), has been partially described [13], [14]. The open reading frame (ORF) of SmSP1 comprises two non-proteolytic domains, followed by a C-terminal trypsin protease domain.…”

Kinins and Their Receptors in Infectious Diseases

“…A study identified a serine protease from S. mansoni cercariae genomic DNA: a kallikrein-like protease [ 176 ]. The same research group isolated the serine protease SmSP1 from S. mansoni , which presents homology with mouse plasma kallikrein and human factor I light chain.…”