1,3-D-半乳糖基转移酶p.Arg187Cys突变导致形成ABx亚型

目的既往在中国人群中发现的1,3-D-半乳糖基转移酶p.Arg187Cys突变个体表型为正常B型,本文探究该突变导致AB亚型的可能分子机制。方法利用免疫血清学方法鉴定一名中国籍个体的血型血清型,PCR方法扩增ABO基因增强子、启动子和所有7个外显子及其侧翼序列,并对扩增产物进行测序分析;采用Chimira软件构建3D分子模型,就突变对1,3-D-半乳糖基转移酶结构的影响进行预测。结果经血清学方法鉴定为ABx亚型。对ABO基因测序显示,该健康个体为A1.02/B.03基因型;仅在B等位基因第7外显子检出c.559C>T(p.Arg187Cys)突变,ABO基因其余位点未见突变。3D分子模型分析提示p.Arg187Cys突变改变了1,3-D-半乳糖基转移酶局部的氢键网络,可能因此导致酶活性下降;在与A基因共表达时,在1,3-N-乙酰氨基半乳糖转移酶的竞争作用下表现出弱B表型。结论ABO*B基因c.559C>T突变通过减弱1,3-D-半乳糖基转移酶的活性以及ABO*A基因产物的竞争作用而导致形成ABx亚型。

ABx Subtype Formation by 1,3-D-Galactosyltransferase p.Arg187Cys Mutation

Objective The phenotype of 1,3-D-galactosyltransferase p.Arg187Cys mutation previously found in Chinese population is normal B type.This study aims to explore the possible molecular mechanism of AB subtype induced by this mutation.Methods We identified the blood group and serotype of a Chinese individual by immunoserology.The enhancer,promoter,all seven exons and flanking sequences of ABO gene were amplified by PCR,and the amplified products were sequenced.The 3D molecular model was constructed by chimera software to predict the effect of mutation on the structure of 1,3-D-galactosyltransferase.Results It was identified as ABx subtype by serological method.The ABO gene sequencing showed that this healthy individual was A1.02/B.03 genotype;Only c.559C>T(p.Arg187Cys)mutation was detected in exon 7 of allele B,and no mutation was found in the rest of ABO gene.The 3D molecular model analysis showed that p.Arg187Cys mutation changed the local hydrogen bonding network of 1,3-D-galactosyltransferase,which may decrease enzyme activity.When co-expressed with A gene,it showed weak B phen-otype under the competition of 1,3-N-acetylgalactosamine transferase.Conclusions The c.559C>T mutation of ABO*B gene leads to the formation of ABx subtype by weakening the activity of 1,3-D-galactosyltransferase and the competition of ABO*A gene products.