The nature of the common erythrocyte antigens En a FR and Wr b , that are both absent from En(a-) cells, and the rare Wr a receptor, apparently encoded by an allele of Wr b 9 was investigated. Various modification, fractionation or cleavage products of erythrocyte membranes were used in hemagglutination inhibition assays. The En a FR and Wr b antigens were shown to represent labile structures within the residues approx. 62-72 of the major (MN) sialoglycoprotein that require lipids, at least for complete expression of antigenic activity. During the course of these experiments, the arrangement of the MN glycoprotein's peptide chain with respect to the lipid bi-layer was also studied, using various proteinases. Furthermore, the MN glycoprotein was found to aggregate with the major membrane protein (band 3) in the presence of Triton X-100. The Wr a antigen was shown to exhibit properties that differ considerably from those of the Wr b receptor. Analyses on the MN glycoprotein, isolated from the red cells of the only known Wr° homozygote and two Wr*Wr b individuals, did not reveal any amino-acid exchange within the residues 40-96 of the molecule. Therefore, the Wr locus that determines the presence or absence of the Wr b antigen on the MN glycoprotein might influence the posttranslational modification of amino-acid residues, the structure of tightly bound lipids or the aggregation of the MN glycoprotein with a different protein such as band 3.
Hochfrequente Antigene auf menschlichen Erythrozytenmembran-Sialoglycoproteinen, III. Untersuchungen an den En a FR-, Wr b -und Wi*-AntigenenZusammenfassung: Die Eigenschaften der häu-figen Erythrozytenantigene En a FR and Wr b , die beide in En(a-) Zellen fehlen, und des seltenen Wr a Rezeptors, der offensichtlich durch ein Allel von Wr b kodiert wird, wurden untersucht. Diverse Modifizierungs-, Fraktionierungs-und