Huang Yuxiang, Qiao Fei, Abagyan Ruben, Hazard Starr, Tomlinson Stephen
Department of Microbiology and Immunology, Medical University of South Carolina, South Carolina 29403, USA.
J Biol Chem. 2006 Sep 15;281(37):27398-404. doi: 10.1074/jbc.M603690200. Epub 2006 Jul 14.
CD59 is a membrane glycoprotein that regulates formation of the cytolytic membrane attack complex (MAC or C5b-9) on host cell membranes. It functions by binding to C8 (alpha chain) and C9 after their structural rearrangement during MAC assembly. Previous studies indicated that the CD59 binding site in C9 was located within a 25-residue disulfide-bonded loop, and in C8alpha was located within a 51-residue sequence that overlaps the CD59 binding region of C9. By peptide screens and the use of peptides in binding assays, functional assays, and computer modeling and docking studies, we have identified a 6-residue sequence of human C9, spanning residues 365-371, as the primary CD59 recognition domain involved in CD59-mediated regulation of MAC formation. The data also indicate that both C8alpha and C9 bind to a similar or overlapping site on CD59. Furthermore, data from CD59-peptide docking models are consistent with the C9 binding site on CD59 located at a hydrophobic pocket, putatively identified previously by CD59 mutational and modeling studies.
CD59是一种膜糖蛋白，可调节宿主细胞膜上溶细胞性膜攻击复合物（MAC或C5b-9）的形成。它在MAC组装过程中通过在C8（α链）和C9结构重排后与之结合来发挥作用。先前的研究表明，C9中的CD59结合位点位于一个25个残基的二硫键连接环内，而在C8α中位于一个51个残基的序列内，该序列与C9的CD59结合区域重叠。通过肽筛选以及在结合测定、功能测定以及计算机建模和对接研究中使用肽，我们确定了人C9的一个6个残基的序列，跨越365-371位残基，作为参与CD59介导的MAC形成调节的主要CD59识别结构域。数据还表明，C8α和C9都与CD59上的相似或重叠位点结合。此外，来自CD59-肽对接模型的数据与CD59上的C9结合位点位于一个疏水口袋一致，该口袋先前通过CD59突变和建模研究推测确定。
