Ultrastructural and biochemical detection of biotin and biotinylated polypeptides in Schistosoma mansoni

Abstract

Biotinylation is proposed for the identification of surface proteins in Schistosoma mansoni using the streptavidin-HRP conjugate for the detection of labeled polypeptides. However, control samples also showed several endogenous biotinylated polypeptides. In an attempt to determine the possibility of nonspecific binding between the streptavidin-HRP conjugate and polypeptides from S. mansoni, the conjugate was blocked with biotinamidecaproate-N-hydroxysuccinimide ester (BcapNHS) before biotin-streptavidin blotting. No bands were detected on the nitrocellulose sheet, demonstrating the specific recognition of biotin by the streptavidin present in the conjugate. Whole cercariae and cercarial bodies and tails showed several endogenous biotinylated polypeptides. The biotin concentration was 13 µg/ 190,000 cercariae. Adult worms presented less endogenous biotinylated polypeptides than cercariae. These results may be due to changes in the environment from aerobic to anaerobic conditions when cercarial bodies (schistosomula) are transformed into adult worms and a decrease in CO 2 production may occur. Cercariae, cercarial bodies and adult male worms were examined by transmission electron microscopy employing an avidin-colloidal gold conjugate for the detection of endogenous biotin. Gold particles were distributed mainly on the muscle fibers, but dispersed granules were observed in the tegument, mitochondria and cytosol. The discovery of endogenous biotin in S. mansoni should be investigated in order to clarify the function of this vitamin in the parasite.

Schistosoma mansoni excretory secretory products induce protein kinase signalling, hyperkinesis, and stem cell proliferation in the opposite sex

“…Our attempts to purify and characterise the biotinylated ESPs that bound the worm teguments were hampered to some extent by endogenous biotinylated proteins being present at the tegument surface. While endogenous biotin has been previously demonstrated in S. mansoni tissues by transmission electron microscopy 60 , our fluorescence microscopy data also point to the presence of this vitamin at the surface of the adult worm. These findings have implications for biotinylation-based studies that aim at isolating Schistosoma surface proteins for proteomic analysis [61][62][63] .…”