Nucleotide and amino acid sequence of exon 4B (underlined capital letters) of the variant TβRIIC and TβRIICΔ4 are given. Furthermore, the partial nucleotide and amino acid sequences of TβRII without exon 4B are shown. Bold letters mark the amino acid and nucleotide exchanges with respect to the human sequence. Arrows indicate the exon boundaries. (hs, homo sapiens; pt, pan troglodytes; mmu, macaca mulatta).