Structure of the human C6 gene.
The terminal components of the complement system (C6-C9) are related proteins, differing in size and complexity. They seem to be typical mosaic proteins, composed of modules which are homologous with parts of other proteins. Individual elements in a mosaic protein are often bounded by introns in the gene, and where they are duplicated within a polypeptide, partial gene duplication within the gene is responsible. It is often found in such genes that the intron/exon boundaries are of the class 1 type. We have examined the boundaries of 17 of the 18 exons of C6 and five of C7. When considered with published data for C9, only one of the protein elements appears to follow the conventional pattern. These data suggest a more complex evolutionary history for the genes of the terminal complement components than had been anticipated and challenge the notions both that discovery of a recognized protein module is of predictive value in relation to gene structure and that these genes evolved from the simple to the complex.
MIP Unit, MRC Centre, Cambridge, U.K.
M J
MJ
Hobart
B
B
Fernie
R G
RG
DiScipio
D000595:Amino Acid Sequence; D001483:Base Sequence; D003183:Complement C6 / Q000235:genetics*; D003184:Complement C7 / Q000235:genetics; D004247:DNA; D005091:Exons; D006801:Humans; D007438:Introns; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D015183:Restriction Mapping
D003183:Complement C6; D003184:Complement C7; D004247:DNA