Sanders S K, Fox R O, Kavathas P
Department of Laboratory Medicine, Yale University, New Haven, Connecticut 06510.
J Exp Med. 1991 Aug 1;174(2):371-9. doi: 10.1084/jem.174.2.371.
The T cell co-receptor, CD8, binds to the alpha 3 domain of HLA class I (Salter, R.D., R.J. Benjamin, P.K. Wesley, S.E. Buxton, T.P.J. Garrett, C. Clayberger, A.M. Krensky, A.M. Norman, D.R. Littman, and P. Parham. 1990. Nature [Lond.]. 345:41; Connolly, J.M., T.A. Potter, E.M. Wormstall, and T.H. Hansen. 1988. J. Exp. Med. 168:325; and Potter, T.A., T.V. Rajan, R.F. Dick II, and J.A. Bluestone. 1989. Nature [Lond.]. 337:73). To identify regions of CD8 that are important for binding to HLA class I, we performed a mutational analysis of the CD8 molecule in the immunoglobulin (Ig)-like variable domain. Our mutational analysis was based on our finding that using a cell-cell adhesion assay murine CD8 (Lyt-2) did not bind to human class I. Since the interaction of human CD8 with HLA class I is species specific, we substituted nonconservative amino acids from mouse CD8 and analyzed the ability of the mutated CD8 molecules expressed in COS 7 cells to bind HLA class I-bearing B lymphoblastoid cells, UC. Mutants with the greatest effect on binding were located in a portion of the molecule homologous to the first and second hypervariable regions of an antibody combining site. In addition, a panel of 12 anti-CD8 monoclonal antibodies were used to stain the 10 CD8 mutants, and amino acids that affected antibody binding were localized on the crystal structure of the Bence-Jones homodimer, REI. Support for an Ig-like structure of CD8 can be found in the pattern of substitutions affecting antibody binding. This work supports the similar tertiary structure of the CD8 alpha-terminal domain and an Ig variable domain.
T细胞共受体CD8与HLA I类分子的α3结构域结合(索尔特,R.D.,R.J.本杰明,P.K.韦斯利,S.E.巴克斯顿,T.P.J.加勒特,C.克莱伯格,A.M.克伦斯基,A.M.诺曼,D.R.利特曼,以及P.帕尔哈姆。1990年。《自然》[伦敦]。345:41;康诺利,J.M.,T.A.波特,E.M.沃姆斯塔尔,以及T.H.汉森。1988年。《实验医学杂志》。168:325;以及波特,T.A.,T.V.拉詹,R.F.迪克二世,以及J.A.布卢斯托。1989年。《自然》[伦敦]。337:73)。为了确定CD8中对于与HLA I类分子结合很重要的区域,我们对免疫球蛋白(Ig)样可变结构域中的CD8分子进行了突变分析。我们的突变分析基于我们的发现,即使用细胞 - 细胞黏附试验时,小鼠CD8(Lyt - 2)不与人I类分子结合。由于人CD8与HLA I类分子的相互作用具有种属特异性,我们用来自小鼠CD8的非保守氨基酸进行替换,并分析在COS 7细胞中表达的突变CD8分子与携带HLA I类分子的B淋巴母细胞系UC结合的能力。对结合影响最大的突变体位于分子中与抗体结合位点的第一和第二高变区同源的部分。此外,使用一组12种抗CD8单克隆抗体对10个CD8突变体进行染色,并将影响抗体结合的氨基酸定位在本斯·琼斯同二聚体REI的晶体结构上。在影响抗体结合的替换模式中可以找到对CD8具有Ig样结构的支持。这项工作支持了CD8α末端结构域与Ig可变结构域相似的三级结构。