Serologic and molecular identification of the variation on ABO*B.01 gene in ABO glycosyltransferases associated with Bw phenotype: a case report

AB antigen is formed by glycosyltransferase enzyme, which catalyzes the corresponding substrates to be connected to the galactose of the precursor substance H antigen. To study the effect of the α-1,3-D galactosyltransferase (GTB) gene mutation on B antigen expression, we explored its molecular mechanism by combining molecular biological methods with bioinformatics. The ABO blood type of the patients was identified using conventional serologic methods, and the polymerase chain reaction (PCR) products of exons 1-7 of the ABO gene were directly sequenced using gene-specific primers and direct sequencing. Proteins in the secretory supernatant of transfected cells were collected in vitro, and GTB content was quantitatively analyzed using western blotting. Bioinformatics software was used to simulate the 3-dimensional structure of the mutant protein. In this case, the patient's serologic test results revealed subtype B. Gene sequencing results confirmed a mutation at base 278 of exon 6. The mutation (c.278C>T) changed the 93rd amino acid of the protein polypeptide chain from proline to leucine (p.P93L). The variant p.P93L did not affect the expression and secretion of GTB, but affected enzyme activity and stability, ultimately manifesting as weakened expression of the B antigen and reduced affinity.