Figure 1. Sequence features of C4 genes and C4 proteins.

(A) Positions of C4A and C4B genomic sequence features shown for a long-form of C4. Exon positions are marked in black, the HERV retroviral sequence is marked in red, and select sequence variants are shown above the exons. Positions are based on the C4 alignment reference, which includes 5’UTR and 3’UTR sequence. The C-del variant and the CT-ins variant are frame-shift mutations that result in premature terminations. (B) Positions of C4A/C4B protein sequence features. The major chains, α, β, and γ, are shown in the bottom row, the cleavage products, C4a and C4d, are shown on the middle row, and important binding locations and sequence variants are shown in the top row. The amino acid positions include the leading 19 amino acid signal peptide.