Abstract: Abstract:Objective To identify and investigate B(A)02 allele in a patient. Methods Serological tests were performed with standard serological methods in a patient with B(A)02 allele. DNA sequences of all seven exons and exon - ntron boundaries of ABO gene were analyzed by polymerase chain reaction (PCR), direct DNA sequencing and sequencing after gene cloning. In order to analyze the allele, PyMOL software was used to establish 3D model of Glycosyltransferases B GTB). Results The serological results showed the characteristics of B(A) phenotype. DNA analysis revealed that ABO gene of the individual was heterozygous of B(A)02/O01 allele. 700C＞G mutation was identified in B101 allele, which resulted in the amino acid substitution P234A in GTB. Through the analysis of the 3D structure of GTB, it was speculated hat the P234A replacement affected the intermolecular forces of the 234 amino acid and Met- 266, thus changed the conformation of the donor-binding pocket of GTB， that made GTB capable of recognizing and tranferring the GalNac to the H antigen, which can lead to the formation of the weak A antigen on membrane of red blood cells. Conclusion The P234A replacement can affect the spatial conformation of the specific recognition region conformed by Met- 266 and Ala- 268 residues, which leads to the antigenicity change of the ABO blood group.

Key words: ABO blood-group system, alleles, B(A) subgroup, PyMOL software