[Molecular Biological Analysis of ABO Blood Group A_el and B_el Subtype]

The molecular biology of alleles of ABO blood group A_el and B_el subtype from two samples was analyzed to explore the effect of mutations on the structure of glycosyltransferase.

The ABO phenotypes were identified by serological techniques, then exons 6 and 7 of ABO gene were amplified and sequenced, combined with haplotype analysis to determine the genotypes. Finally, homology modeling of the mutated A/B glycosyltransferase were conducted by Modeller software and the effect of mutations on the spatial structure was analyzed by PyMol software.

The serological phenotypes of the two samples were A_el and B_el, and their genotypes were ABO*AW.37/ABO*O.01.01 and ABO*BEL.03/ABO*O.01.01, respectively. The three-dimensional structure modeling of the protein showed that, compared to the wild-type glycosyltransferase, two hydrogen bonds between the side chain of p.Glu314 and surrounding amino acid disappeared in the p.Lys314Glu mutant GTA; the hydrogen bonds between the side chain of p.Trp168 and surrounding amino acid also disappeared, and the hydrogen bond between the main chain of p.Trp168 and p.Gly165 was shortened to 3.3 Å in the p.Arg168Trp mutant GTB.

Mutations in exon 7 of ABO gene c.940A>G and c.502C>T are keys to the formation of AW.37 and BEL.03 alleles, resulting in decreased expression of A and B antigens, respectively.