The 45 pocket of HLA-A2.1 plays a role in presentation of influenza virus matrix peptide and alloantigens.
The 45 pocket of HLA-A2.1 plays a role in presentation of influenza virus matrix peptide and alloantigens.
复制标题
HLA-A2.1 的 45 口袋在流感病毒基质肽和同种抗原的呈递中发挥作用。
作者：
C. Winter;B. Carreno;R. Turner;S. Koenig;W. Biddison
将氨基酸取代引入HLA-A2.1的45口袋中，以确定I类分子的这种结构定义特征在病毒肽和同种异体抗原呈递中的潜在作用。45口袋位于α 1-结构域α-螺旋下方，由5个氨基酸组成，其中3个氨基酸在HLA-A2.1和HLA-B37之间不同。这两种I类分子先前已显示具有很大程度上不重叠的肽结合特异性。使用定点诱变将HLA-A2.1的45口袋中的24、45和67位的疏水残基替换为HLA-B37中这些位置中发现的亲水氨基酸。因此，产生了三个单氨基酸突变体：24 A-S、45 M-T和67 V-S。将这些突变体转染到HMy2.C1R细胞中，并评估它们将流感病毒基质M157 -68肽和HTLV-I Tax-12 -25肽呈递给HLA-A2.1限制性肽特异性CTL的能力和将同种抗原呈递给HLA-A2同种特异性CTL系的能力。在45口袋中的这些取代中的每一个产生不能将M1肽呈递给大多数M1肽特异性CTL系的分子。相反，这些突变都不影响Tax-1肽向Tax-1特异性CTL系的呈递，这表明这些突变的HLA-A2分子可以在病毒肽呈递中起作用。45口袋中的三个取代中的两个导致HLA-A2同种特异性CTL系子集缺乏识别。这些结果表明，45口袋中的氨基酸侧链可以强烈影响肽的呈递，并表明45口袋可能在确定肽结合特异性中起作用。
Amino acid substitutions were introduced into the 45 pocket of HLA-A2.1 to determine the potential role of this structurally defined feature of class I molecules in viral peptide and alloantigen presentation. The 45 pocket lies below the alpha 1-domain alpha-helix and is composed of five amino acids, three of which differ between HLA-A2.1 and HLA-B37. These two class I molecules have previously been shown to have largely non-overlapping peptide-binding specificities. Site-directed mutagenesis was used to replace the hydrophobic residues at positions 24, 45, and 67 in the 45 pocket of HLA-A2.1 with the hydrophilic amino acids found in these positions in HLA-B37. Thus, three single amino acid mutants were produced: 24A----S, 45 M----T, and 67V----S. These mutants were transfected into HMy2.C1R cells and assessed for their ability to present influenza virus matrix M1 57-68 peptide and HTLV-I Tax-1 2-25 peptide to HLA-A2.1-restricted, peptide-specific CTL and to present alloantigens to HLA-A2-allospecific CTL lines. Each of these substitutions in the 45 pocket produced a molecule that failed to present the M1 peptide to most M1 peptide-specific CTL lines. In contrast, none of these mutations affected presentation of the Tax-1 peptide to Tax-1-specific CTL lines, which indicates that these mutant HLA-A2 molecules can function in viral peptide presentation. Two of the three substitutions in the 45 pocket resulted in lack of recognition by a subset of HLA-A2 allospecific CTL lines. These results demonstrate that the amino acid side chains in the 45 pocket can strongly influence peptide presentation and suggest that the 45 pocket may play a role in determining peptide-binding specificity.