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Eukaryotic ribosomes that lack a 5.8S RNA.

The 5.8S ribosomal RNA is believed to be a universal eukaryotic characteristic. It has no (size) counterpart among the prokaryotes, although its sequence is homologous with the first 150 or so nucleotides of the prokaryotic large subunit (23S) ribosomal RNA. We report here an exception to this rule. The microsporidian Vairimorpha necatrix is a eukaryote that has no 5.8S rRNA. As in the prokaryotes, it has a single large subunit rRNA, whose 5' region corresponds to the 5.8S rRNA.

Animals↗
PubMed1982

The three cortical membranes of the gregarines (parasitic protozoa). Characterization of the membrane proteins of gregarina blaberae.

GREGARINES, WHICH ARE PARASITIC PROTOZOA LIVING IN INVERTEBRATES, POSSESS A CORTICAL STRUCTURE SPECIFIC TO THEIR VEGETATIVE STAGE: namely two additional cytomembranes are lying just under the plasma membrane. This cortical complex has been isolated by centrifugation on discontinuous sucrose gradients and characterized chemically. Its integrity was tested by electron microscopy. Ghost proteins were resolved by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. About 30 polypeptides of mol.wt. 15000-300000 were present in this fraction and four glycoproteins were detected after periodate/Schiff staining. Ten major proteins were labelled after lactoperoxidase-catalysed iodination. The GP(2) glycoprotein (41000-49000 apparent mol.wt.) appears to be a major component of the cell surface. Effects of trypsin and Pronase digestion on ghosts and cells were monitored by gel electrophoresis and by electron microscopy. Ghosts treated with low trypsin or Pronase concentrations (10-25mug/ml) became drastically disorganized; many proteins were vigorously attacked in comparison with those of control ghosts. Variations in proteinase-sensitivity of proteins are pointed out. The GP(3) glycoprotein (130000-160000 apparent mol.wt.) seemed to be the only glycoprotein released from the cell surface by trypsin. Whole cells treated under the same conditions or with higher proteinase concentrations (up to 1mg/ml) do not exhibit morphological modifications of the cell surface; furthermore, no discernible cleavage of membrane proteins was indicated by electrophoretograms. It is postulated that cell-surface proteins are protected by the dense carbohydrate cell coat. By using various different methods (change of ionic strength, detergent, denaturing agent, labelling experiment) it was possible to localize several major proteins within the protozoon cortical membranes.

Animals↗
PubMed1987

Comparison of arylsulphatases from Eimeria tenella (parasite) and chicken caecum (host).

Chicken caecal arylsulphatase was purified 700-fold by (NH4)2SO4 fractionation, concanavalin A-Sepharose and cyclic AMP-Sepharose chromatographies. The purified enzyme was a glycoprotein of Mr 97,000. It hydrolysed p-nitrocatechol sulphate, cerebroside 3-sulphate and ascorbic acid 2-sulphate and was strongly inhibited by Na2SO4 (Ki = 50 microM) and Na3PO4 (Ki = 20 microM). Arylsulphatase from Eimeria tenella sporozoites was purified 28-fold by (NH4)2SO4 fractionation. Arylsulphatase of E. tenella sporozoites was not a glycoprotein. It had an Mr of 49,000. It was inhibited by Na2SO4 (Ki = 300 microM), sodium phosphate (Ki = 90 microM) and heparin. It hydrolysed ascorbic acid 2-sulphate, but cerebroside 3-sulphate was not desulphated. The kinetic parameters of chicken caecal arylsulphatase were different from those of the E. tenella enzyme.

Animals↗