1例B(A)02等位基因的鉴定及分子机制研究

Identification and molecular mechanism study of a case with B(A)02 allele

目的 B(A)02等位基因的鉴定及分子机制的研究。方法对1例B(A)02等位基因者ABO血清学定型使用标准血清学实验方法,对ABO基因7个外显子及其侧翼序列做PCR扩增、基因克隆和测序分析;使用Py MOL软件建立B糖基转移酶(GTB)的空间模型并进行分析。结果血清学检测结果符合B(A)亚型特点,DNA克隆和测序分析显示被检者为B(A)02/O01杂交基因,在B101等位基因上存在700C>G错义突变,导致GTB发生P234A氨基酸置换。通过对GTB空间结构的分析,认为P234A置换影响了第234位氨基酸与Met-266的分子间作用力,从而改变了GTB识别供糖体的结合凹槽的结构,使GTB能够结合并转移N-乙酰氨基半乳糖(Gal Nac)至底物H抗原,从而在红细胞膜上形成弱A抗原。结论 P234A的置换影响了决定GTB识别特异性的Met-266与Ala-268所组成的特异性识别区域的空间结构,从而改变了ABO血型的抗原性。

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-intron 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 that 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.