1iw2
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X-ray structure of Human Complement Protein C8gamma at pH=7.O
OverviewOverview
C8gamma is a 22-kDa subunit of human C8, which is one of five components, of the cytolytic membrane attack complex of complement (MAC). C8gamma is, disulfide-linked to a C8alpha subunit that is noncovalently associated, with a C8beta chain. In the present study, the three-dimensional structure, of recombinant C8gamma was determined by X-ray diffraction to 1.2 A, resolution. The structure displays a typical lipocalin fold forming a, calyx with a distinct binding pocket that is indicative of a, ligand-binding function for C8gamma. When compared to other lipocalins, the overall structure is most similar to neutrophil gelatinase associated, lipocalin (NGAL), a protein released from granules of activated, neutrophils. Notable differences include a much deeper binding pocket in, C8gamma as well as variation in the identity and position of residues, lining the pocket. In C8gamma, these residues allow ligand access to a, large hydrophobic cavity at the base of the calyx, whereas corresponding, residues in NGAL restrict access. This suggests the natural ligands for, C8gamma and NGAL are significantly different in size. Cys40 in C8gamma, which forms the disulfide bond to C8alpha, is located in a partially, disordered loop (loop 1, residues 38-52) near the opening of the calyx., Access to the calyx may be regulated by movement of this loop in response, to conformational changes in C8alpha during MAC formation.
About this StructureAbout this Structure
1IW2 is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of human complement protein C8gamma at 1.2 A resolution reveals a lipocalin fold and a distinct ligand binding site., Ortlund E, Parker CL, Schreck SF, Ginell S, Minor W, Sodetz JM, Lebioda L, Biochemistry. 2002 Jun 4;41(22):7030-7. PMID:12033936
Page seeded by OCA on Mon Nov 12 17:35:16 2007