p.R180C mutation of glycosyltransferase B leads to B subgroup, an in vitro and in silico study

Molecular Basis of ABO Variants Including Identification of 16 Novel ABO Subgroup Alleles in Chinese Han Population

Introduction

The characteristic of ABO blood subgroup is crucial for elucidating the mechanisms of such variant phenotypes and offering useful information in blood transfusion.

Methods

In total, 211 ABO variants including part of available family members were investigated in this study. The phenotypes of these individuals were typed with serologic methods. The full coding regions of ABO gene and the erythroid cell-specific regulatory elements in intron 1 of them were amplified with polymerase chain reaction and then directly sequenced. The novel alleles were confirmed by cloning and sequencing. Phylogenetic tree was made using CLUSTAL W software. 3D structural analyses of the glycosyltransferases (GTs) with some typical mutations were performed by PyMOL software.

Results

Forty-eight distinctly rare ABO alleles were identified in 211 Chinese variant individuals, including 16 novel ABO alleles. All of the alleles were categorized as 5 groups: 16 ABO*A alleles, 23 ABO*B alleles, 4 ABO*BA alleles, 4 ABO*cisAB alleles, and 1 ABO*O alleles. ABO*A2.08 and ABO*BA.02 were the relatively predominant A and B subgroup alleles, respectively. According to the phylogenetic tree, 28 alleles (5 common alleles and 23 alleles identified in our laboratory) were classified into 3 major allelic lineages. The structural analysis of 3D homology modeling predicted reduced protein stability of the mutant GTs and may explain the reduced ABO antigen expression.

Conclusions

The molecular basis of ABO variants was analyzed, and 16 novel ABO alleles were identified. The results extended the information of ABO variants and provided a basis for better transfusion strategies and helped to improve blood transfusion safety.

An unexpected dynamic binding mode between coagulation factor X and Rivaroxaban reveals importance of flexibility in drug binding

Rivaroxaban (RIV) is a direct oral anticoagulant (DOAC) targeting activated coagulation factor X (FXa). An earlier study reported the F174A mutant of FXa resistant to a RIV-like inhibitor, Apixaban. In current study, the detailed molecular mechanism of the resistance has been explored by molecular dynamics simulations on the impaired interactions between RIV and FXa in the damaged S4 pocket of F174A mutant. Besides, an unexpected relative stable binding mode of S1'S1 was revealed, which required dynamic motions of Gln192 and Gln61 to allow the morpholinone moiety of RIV to shift into the S1' pocket and form strong interactions. These dynamic motions of RIV and critical residues might be important in drug design for direct inhibitors of coagulation factors.

Molecular genetic analysis of weak ABO subgroups in the Chinese population reveals ten novel ABO subgroup alleles

BACKGROUND

A weak ABO subgroup is one of the most important causes of an ABO blood grouping discrepancy. Here, we investigated the distribution of weak ABO subgroups in the Chinese population and identified ten novel weak ABO subgroup alleles.

MATERIAL AND METHODS

We performed phenotype investigations by serological studies, analysed the DNA sequence of the ABO gene by direct sequencing or sequencing after cloning, and evaluated the role of glycosyltransferase mutations by in silico analysis and in vitro expression assay.

RESULTS

Three hundred and fifty-one individuals with a weak ABO subgroup were detected among 1.45 million blood-typed subjects. Ten novel weak ABO subgroup alleles were identified. Molecular modelling and analysis of GTA mutation p.L339P suggested that the mutation may change the local conformation of GTA and reduce its stability. The in vitro expression assay showed that A antigen expression and agglutination of HeLa cells transfected with GTA mutant p.L339P decreased significantly compared to those of cells transfected with wild-type GTA.

CONCLUSION

Ten novel weak ABO subgroup alleles were identified in the Chinese population. GTA mutant p.L339P may lead to a weak A phenotype by changing the local conformation of GTA and reducing its stability.