title: Defining the CD59-C9 binding interaction.
abstract: 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.
authors.affiliation: Department of Microbiology and Immunology, Medical University of South Carolina, South Carolina 29403, USA.
authors.forename: Yuxiang
authors.initials: Y
authors.lastname: Huang
authors.forename: Fei
authors.initials: F
authors.lastname: Qiao
authors.forename: Ruben
authors.initials: R
authors.lastname: Abagyan
authors.forename: Starr
authors.initials: S
authors.lastname: Hazard
authors.forename: Stephen
authors.initials: S
authors.lastname: Tomlinson
mesh_terms: D001665:Binding Sites; D018957:CD59 Antigens / Q000096:biosynthesis*; D003186:Complement C9 / Q000737:chemistry*; D019295:Computational Biology; D004252:DNA Mutational Analysis; D006031:Glycosylation; D006801:Humans; D008958:Models, Molecular; D019151:Peptide Library; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D012984:Software
chemical_list: D018957:CD59 Antigens; D003186:Complement C9; D019151:Peptide Library; D010455:Peptides; D011994:Recombinant Proteins