Fig. 1. Sequence comparison of the carboxy-terminal domain of CEA gene family members: (a) Nucleotides. Underlined bases are stop codons, and dashes show a naturally occurring base deletion in comparison with the CEACAM1 gene. (b) Amino acids. Underlined amino acids are the known GPI anchor attachment sites and stars show the position of stop codons. Bold letters indicate the position of amino acid mutations in various constructed, mutant CC1-4L proteins. The TM domain of mutant GPI-linked CC1-tAT protein and the positions of its mutations (bold letters) are also shown in b for comparison.