title: Diazotised [125I]iodosulphanilic acid is not a marker for the outer bilayer of the tegument of adult Schistosoma mansoni.
abstract: Diazotised [125I]iodosulphanilic acid (DISA), has been used to label the tegument surface of adult male Schistosoma mansoni in vitro. In a surface membrane fraction prepared by freeze-thaw, only a negligible amount of lipid material was labelled by DISA, and 15 labelled protein bands were detected, ranging in apparent molecular weight from 21,000 to 175,000. As a result of experiments using digitonin to extract surface material, DISA has been described as a marker for the outer bilayer of the schistosome tegument surface. However, we found that two surface membrane fractions obtained by digitonin extraction, which were expected to be enriched in either outer or inner bilayer, yielded almost identical sodium dodecyl sulphate-polyacrylamide gel electrophoresis autoradiographic patterns, with 13 labelled protein bands (21 to 64 kDa) detected in each. In addition, a large proportion of the label was not bound firmly to the worm surface, and although the intact worm surface restricted the access of the label to membrane proteins, nevertheless proteins of the inner bilayer were labelled. Thus, we conclude that DISA is not a marker for the outer bilayer.
authors.affiliation: Department of Biology, University of York, U.K.
authors.forename: N
authors.initials: N
authors.lastname: Saunders
authors.forename: S M
authors.initials: SM
authors.lastname: Roberts
authors.forename: R A
authors.initials: RA
authors.lastname: Wilson
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001345:Autoradiography; D003720:Densitometry; D003979:Diazonium Compounds; D004072:Digitonin; D004591:Electrophoresis, Polyacrylamide Gel; D005615:Freezing; D008297:Male; D008565:Membrane Proteins / Q000032:analysis*; D012550:Schistosoma mansoni / Q000032:analysis* / Q000201:enzymology / Q000648:ultrastructure
chemical_list: D003979:Diazonium Compounds; D008565:Membrane Proteins; C018909:diazoiodosulfanilic acid; D000469:Alkaline Phosphatase; D004072:Digitonin