[Molecular mechanism underlying an individual with with Ael subtype due to a novel p.Tyr264Cys variant of α-1, 3-N-acetylgalactosaminotransferase gene].

OBJECTIVE

To explore the molecular mechanism underlying a novel Ael subtype due to a p.Tyr264Cys variant of the α-1, 3-N-acetylgalactosaminotransferase gene.

METHODS

The ABO blood type of the individual was confirmed by serological methods. All exons and adjacent intron regions of the ABO gene were amplified with PCR and sequenced. Prime-specific single-strand amplification and sequencing analysis were performed on the regions harboring the variant sites. Bioinformatics tools including Pymol, DUET, PolyPhen-2 and PROVEAN were used to analyze the effect of the novel variant on the structure and function of the enzyme.

RESULTS

The absorption and release test had detected extremely weak A antigen on the surface of red blood cells, confirming an Ael phenotype. Primer-specific haploid sequencing analysis revealed a c.791A>G missense variant on the A allele, which resulted in a p.Tyr264Cys amino acid change in the α-1,3-N-acetylgalactosaminotransferase. Molecular modeling revealed that the p.Tyr264Cys variant can weaken the local hydrogen bond network of the protein. Meanwhile, the predicted free energy change (ΔΔG) was negative, both suggesting a decrease in protein stability. PolyPhen-2 and PROVEAN respectively predicted the p.Tyr264Cys variant as probably damaging and deleterious.

CONCLUSION

The novel p.Tyr264Cys variant of the α-1, 3-N-acetylgalactosaminotransferase may cause instability in the structure and function of the enzyme, leading to the Ael subtype.