C8gamma is a 22-kDa subunit of @entity1 C8, which is one of five components of the cytolytic membrane attack complex of complement (MAC). C8gamma is @entity1520 -linked to a @entity37672 subunit that is noncovalently associated with a @entity37673 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 @entity15901 ( @entity15901 ), 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 @entity15901 restrict access. This suggests the natural ligands for C8gamma and @entity15901 are significantly different in size. @entity2569 40 in C8gamma, which forms the @entity1520 bond to @entity37672 , 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 @entity37672 during MAC formation.

Crystal structure of XXXX complement protein C8gamma at 1.2 A resolution reveals a lipocalin fold and a distinct ligand binding site.

@entity1 :: ('9606', 'Species') :: ['human'] @entity37673 :: ('732', 'Gene') :: ['C8beta'] @entity2569 :: ('CHEBI:17561', 'Chemical') :: ['Cys'] @entity37672 :: ('731', 'Gene') :: ['C8alpha'] @entity1520 :: ('CHEBI:48343', 'Chemical') :: ['disulfide'] @entity15901 :: ('3934', 'Gene') :: ['NGAL', 'neutrophil gelatinase associated lipocalin']
@entity1 :: (9606,Species) :: ['human']
