1IW2

X-ray structure of Human Complement Protein C8gamma at pH=7.O

Summary for 1IW2

• Entry DOI: 10.2210/pdb1iw2/pdb
• Related: 1LF7
• Descriptor: Complement Protein C8gamma (2 entities in total)
• Functional Keywords: lipocalin, beta barrel, calyx, mac, complement, immune system
• Biological source: Homo sapiens (human)
• Cellular location: Secreted: P07360
• Total number of polymer chains: 1
• Total formula weight: 20305.98

Authors

Ortlund, E.,Parker, C.L.,Schreck, S.F.,Ginell, S.,Minor, W.,Sodetz, J.M.,Lebioda, L. (deposition date: 2002-04-11, release date: 2002-06-12, Last modification date: 2024-11-13)

Primary citation

Ortlund, E.,Parker, C.L.,Schreck, S.F.,Ginell, S.,Minor, W.,Sodetz, J.M.,Lebioda, L.
Crystal structure of human complement protein C8gamma at 1.2 A resolution reveals a lipocalin fold and a distinct ligand binding site.
Biochemistry, 41:7030-7037, 2002

PubMed Abstract: 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.

PubMed: 12033936
DOI: 10.1021/bi025696i

Experimental method

X-RAY DIFFRACTION (1.9 Å)