Sequence homology of complement C8 gamma chain with alpha 1-microglobulin and its implications for C8 structure and function.
Complement C8 gamma is a disulphide bonded subunit of C8 with no known homology or function. We show here that it strongly resembles alpha 1-microglobulin and protein HC in both length and sequence suggesting a common genetic origin. By extrapolation from the alpha 1-microglobulin family we are able to suggest that the cysteine residue of C8 gamma is involved in disulphide bonding to C8 alpha, and a possible physiological role in the regulation of the inflammatory response. Comparison of C8 gamma with C8 alpha shows that one region of C8 alpha bears a structural homology with the region of C8 gamma containing the free cysteine residue. This homology includes a cysteine residue of C8 alpha, for which no equivalent is found in C8 beta or C9, and which is therefore a likely candidate for C8 gamma attachment.
Luzio
J P
JP
European Molecular Biology Laboratory, Heidelberg, FRG.
Stanley
K K
KK
D000510:Alpha-Globulins; D000595:Amino Acid Sequence; D003185:Complement C8; D008969:Molecular Sequence Data; D011480:Protease Inhibitors; D012689:Sequence Homology, Nucleic Acid; D013329:Structure-Activity Relationship
D000510:Alpha-Globulins; D003185:Complement C8; D011480:Protease Inhibitors; C016001:alpha-1-microglobulin