Definition of the complete Schistosoma mansoni hemoglobinase mRNA sequence and gene expression in developing parasites
el Meanawy, M.A.; Aji, T.; Phillips, N.F.; Davis, R.E.; Salata, R.A.; Malhotra, I.; McClain, D.; Aikawa, M.; Davis, A.H.
American Journal of Tropical Medicine and Hygiene 43(1): 67-78
1990
ISSN/ISBN: 0002-9637 PMID: 2382765 Document Number: 361408
Schistosoma mansoni uses a variety of proteases termed haemoglobinases to obtain nutrition from host globin. Previous reports have characterized cDNAs encoding 1 of these enzymes. However, these sequences did not define the primary structures of the mRNA and protein. The complete sequence of the 1390 base mRNA was determined. It encodes a 50 000 MW primary translation product. In vitro translations coupled with immunoprecipitations and Western blots of parasite lysates allowed visualization of the 50 000 MW form. Production of the 31 000 MW mature haemoglobinase from the 50 000 MW species involves removal of both NH2 and COOH terminal residues from the primary translation product. Expression of haemoglobinase mRNA and protein was examined during larval parasite development. Low levels were observed in young schistosomula. After 6-9 days in culture, high haemoglobinase levels were seen which correlated with the onset of red blood cell feeding. Immunoelectron microscopy was employed to examine haemoglobinase location and function. In adult worms the enzyme was associated with the gut lumen and gut epithelium. In cercariae, the protease was observed in the head gland, suggesting new roles for the protease. The expression of haemoglobinase mRNA and protein increased 6-9 days after beginning of culture of young schistosomula of Schistosoma mansoni, the timing corresponding with onset of red blood cell feeding. As determined by immunoelectron microscopy the enzyme was associated with the gut lumen and gut epithelium of adult worms, and also (unexpectedly) with the head gland of cercariae.Carolyn A. Brown.