Abstract.With the use of endless belt fluid electrophoresis, these studies confirm previous reports of two cell populations in PMFP having different mobilities. Our method shows two clearly separated bands, while with the microelectrophoresis method a distinctly bimodal distribution is reported. The abnormal (A) cells show a 33‐ to 42‐percent reduction in mobility and a 47‐ to 48‐percent reduction in sialic acid as compared with standard cells. The serologically normal (N) cell population, on mixture with standard cells and subjected to electrophoresis, exhibits no increase in streak width indicative of increased electrophoretic heterogeneity. This is consistent with the findings in the preceding report of no serological abnormalities in the (N) cells. Results of hematological studies, red cell isozyme determinations and assays of glycolytic enzymes activity were not significantly different between the two cell populations.These observations lead us to suggest that the basic abnormality in PMFP (A) cells (Tn transformation) represents a point mutation involving a single genetic step in erythrocyte membrane glycoprotein biosynthesis. A block in the transfer of terminal D‐galactose to N‐acetylgalactosamine in a substantial proportion of (A) cell heterosaccharides is postulated to be common to all of the serological and biophysical aberrations. This would be consistent with the observed reduction of T, NVG, NHmn(also MHmn), electrostatic charge, sialic acid, and increased ‘saline agglutinability’ in incomplete antisera. The defect in galactose linkage could also leave exposed underlying N‐acetylgalactosamines with the consequent manifestation of AHmn, AD
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