ULTRASTRUCTURAL AND BIOCHEMICAL DETECTION OF BIOTIN AND BIOTINYLATED POLYPEPTIDES IN SCHISTOSOMA-MANSONI

Biotinylation is proposed for the identification of surface proteins i n Schistosoma mansoni using the streptavidin-HRP conjugate for the det ection of labeled polypeptides. However, control samples also showed s everal endogenous biotinylated polypeptides. In an attempt to determin e 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 b iotin-streptavidin blotting. No bands were detected on the nitrocellul ose sheet, demonstrating the specific recognition of biotin by the str eptavidin present in the conjugate. Whole cercariae and cercarial bodi es and tails showed several endogenous biotinylated polypeptides. The biotin concentration was 13 mu g/190,000 cercariae. Adult worms presen ted less endogenous biotinylated polypeptides than cercariae. These re sults may be due to changes in the environment from aerobic to anaerob ic conditions when cercarial bodies (schistosomula) are transformed in to adult worms and a decrease in CO2 production may occur. Cercariae, cercarial bodies and adult male worms were examined by transmission el ectron microscopy employing an avidin-colloidal gold conjugate for the detection of endogenous biotin. Gold particles were distributed mainl y on the muscle fibers, but dispersed granules were observed in the te gument, mitochondria and cytosol. The discovery of endogenous biotin i n S. mansoni should be investigated in order to clarify the function o f this vitamin in the parasite.