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Substitution Glu480Lys in erythroid band 3 corresponds to the Fr a blood group antigen and supports existence of the second ectoplasmic loop of band 3
Author(s) -
Jarolim Petr,
Kalábová Dana,
Reid Marion E.
Publication year - 2004
Publication title -
transfusion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.045
H-Index - 132
eISSN - 1537-2995
pISSN - 0041-1132
DOI - 10.1111/j.1537-2995.2004.03291.x
Subject(s) - band 3 , antigen , extracellular , red blood cell , microbiology and biotechnology , antibody , allele , biology , reticulocyte , chemistry , membrane , biochemistry , gene , erythrocyte membrane , messenger rna , genetics
BACKGROUND: Polymorphisms in extracellular loops of RBC band 3 correspond to antigens of the Diego blood group system. Of the seven putative extracellular loops, no mutations have until recently been found in the second, fifth, and sixth loops. We detected a substitution Glu480Lys that would be located in its second ectoplasmic loop. We hypothesized the substitution may underlie a novel antigen of the Diego system. STUDY DESIGN AND METHODS: IAT was performed using two different multispecific sera containing anti‐Fr a and a series of multispecific sera containing antibodies against other blood group antigens of the Diego blood group system but not agglutinating Fr(a+) RBCs. Biosynthesis of band 3 was studied by RT‐PCR of reticulocyte RNA and electrophoresis of solubilized RBC membranes. Anion exchange function of band 3 was studied by measuring the influx of radiolabeled sulfate. RESULTS: RBCs from the Glu480Lys carrier were agglutinated with sera containing anti‐Fr a and not by sera with specificities for other antigens of the Diego system. We detected identical quantities of mRNA corresponding to the two band‐3 alleles and normal content of band 3 in the RBC membranes, as well as normal sulfate influx into RBCs from the Fr a heterozygote. CONCLUSIONS: We confirmed the previously reported molecular basis of the Fr a antigen, thus providing supportive evidence for the existence of the second extracellular loop of band 3. We also demonstrated that this substitution does not affect mRNA stability, surface expression, and anion exchange function of band 3.