Abstract:

Objective: To investigate the molecular mechanism of A_wB subtype by performing serological and gene detection in a Chinese individual. Methods: One case of A_wB subtype was determined by ABO serology using standard serological method, and 7 exons of ABO gene and their flanks were amplified by PCR, and then cloned and sequenced. Glycosyl Transferase A (GTA) mutants were constructed by Chimera software, and was mapped and analyzed by PyMOL software. Results: Serological identification showed that this individual had A_wB subtype. DNA cloning and gene sequen-cing analysis showed that the A gene from the proband was A cis-expressed allele of A1.02 and A3.03, and the genotype was ABO*Avar/B.01. In the ISBT database, the A allele of this variant should be a novel allele, with missense mutations in c. 467C>T and c. 838C>T, which could result in p.P.156L and p.L.280F amino acid replacement in GTA. Analysis of the spatial structure of GTA showed, p.L280F resulted in the phenotypes, and did not lead to changes in the overall structure of GTA proteins, which altered the hydrogen bond network between amino acid 280 and surrounding amino acid residues, resulting in local conformation changes. Conclusions: A_wB subtype caused by a novel A allele-is reported for the first time. The formation mechanism may be as follows: p.L280F mutations in glycosyltransferases encoded by the A1.02 allele alter the interactions between adjacent amino acids, resulting in reduced activity of the A enzyme,and A_wB subtype occurs when co-expressing with the B allele.

Key words: ABO blood group system, A_wB subtype, Genetic mutation