罕见等位基因HLA-C*08:84碱基序列和蛋白分子三维结构分析

Characterization of a rare HLA-C*08: 84 allele and analysis its 3-D molecular structure

目的鉴定1例人类白细胞抗原(human leukocyte antigen,HLA)罕见等位基因C*08:84,并调查该基因的家系遗传情况,预测分析其氨基酸残基改变在编码蛋白分子三维空间结构影响。方法应用单核苷酸序列分析、序列特异性寡核苷酸探针聚合酶链反应及单等位基因组特异性测序确定HLA-C分型并对该基因的先证者进行家系调查。应用Swiss-Model服务器,Phyre2和FATCAT在线软件对其三级结构进行模拟分析,对差异氨基酸结构和所处位置及可能的影响进行推测。结果家系分析表明HLA-C*08:84来自先证者母亲,与同源性最高的HLA-C*08:01相比较存在g.512G>C(p.Trp147Ser)变异。其编码三级结构模拟分析表明氨基酸变异位置为α2链,该位置参与构成抗原多肽结合凹槽F。C*08:84与C*08:01、C*08:02、C*08:03、C*08:22肽结合区182个氨基酸主链分子间抗原结合槽均方根偏差(RMSD)分别为1.70 nm、1.79 nm、0.71 nm、1.70 nm。结论确认并分析了罕见等位基因C*08:84,对其临床意义进行初步探讨和分析。

Objective To verify a rare allele of human leukocyte antigen(HLA)and analyze its inheritance and 3D molecular structure.Methods PCR-sequence-based typing,PCR-single strand oligonucleotide polymorphism and single allele-specific sequencing were carried out to characterize the rare HLA-C allele and its transmission in the family.Its protein structure was modeled by using SWISS-MODEL,Phyre2 and FATCAT software.Results Analysis indicated that the rare allele(HLA-C*08:84)has transmitted from the proband’s mother and has differed from HLA-C*08:01 by a single base(g.512G>C),resulting in substitution of an amino acid(p.Trp147Ser).Modeling of the 3D structure of the encoded protein indicated that the amino acid residue variation is located at theα2 helix,which participates the formation of pocket F.Modeling of the structures of C*08:84,C*08:01,C*08:02,C*08:03 and C*08:22 has suggested significant variation in the peptide binding regions of the backbone,with root mean square errors being 1.70 nm,1.79 nm,0.71 nm and 1.70 nm,respectively.Conclusion A rare HLA-C*08:84 allele has been identified,and its clinical significance has been analyzed.