ABSTRACT
We have described a drug-responsive form of a cell surface NADH oxidase (hydroquinone oxidase) of cancer cells (tNOX) that exhibits unusual characteristics including resistance to proteases, resistance to cyanogen bromide digestion, and an ability to form amyloid filaments closely resembling those of spongiform encephalopathies and all of which are characteristics of PrP(sc) (PrP(res)), the presumed infective and proteinase K resistant particle of the scrapie prion. The tNOX protein from the HeLa cell surface copurified with authentic glyceraldehyde-3-phosphate dehydrogenase (muscle form) (GAPDH). Surprisingly, the tNOX-associated muscle GAPDH also was proteinase K resistant. In this paper, we show that combination of authentic rabbit muscle GAPDH with tNOX renders the GAPDH resistant to proteinase K digestion. This property, that of converting the normal form of a protein into a likeness of itself, is one of the defining characteristics of the group of proteins designated as prions.
Subject(s)
NADH, NADPH Oxidoreductases/chemistry , NADH, NADPH Oxidoreductases/metabolism , Neoplasm Proteins/chemistry , Neoplasm Proteins/metabolism , Prions/chemistry , Prions/metabolism , Animals , Endopeptidase K/metabolism , Glyceraldehyde-3-Phosphate Dehydrogenases/metabolism , HeLa Cells , Humans , Hydrolysis , Isoenzymes/chemistry , Isoenzymes/genetics , Isoenzymes/metabolism , NADH, NADPH Oxidoreductases/genetics , Neoplasm Proteins/genetics , Peptide Fragments/biosynthesis , Peptide Fragments/genetics , Peptide Fragments/metabolism , PrPSc Proteins/chemistry , PrPSc Proteins/metabolism , Prions/genetics , Rabbits , Recombinant Proteins/biosynthesis , Recombinant Proteins/metabolismABSTRACT
OBJECTIVE: To evaluate a novel fixation system for reproducible radiography in edentulous patients. METHODS: A conventional extra-oral fixation system was modified with a filmholder and adjustable scales. For measuring reproducibility and angulation errors two rods and two balls were fixed on the alveolar crests of the maxilla and the mandible and angular variations were measured. One hundred radiographs of a conventional phantom were taken by one of the authors and by ten dental students. The angular disparity was calculated and intra- and interoperator precision determined. RESULTS: The average time taken to assemble the fixation system was 4 min. The 95% confidence interval for precision of the single operator was less than 2.5 degrees in both the maxilla and mandible. The 95% confidence interval for precision of the ten students was less than 2.2 degrees for the maxilla and 2.7 degrees for the mandible. There was no significant difference (P>0.05) in interoperator precision. CONCLUSION: The novel extra-oral fixation system appears to be a potential means of obtaining reproducible radiographs of edentulous patients.
