Immunological characterization and structural studies of normal fecal antigen-1 related to carcinoembryonic antigen.
Normal fecal antigen-1 (NFA-1), which is a carcinoembryonic antigen (CEA)-related glycoprotein with a mol. wt of 20,000-30,000, was purified from normal adult feces by immuno-adsorption, gel filtration and ion exchange chromatography. Highly purified NFA-1 was partially cross-reactive with CEA but antigenically unrelated to nonspecific cross-reacting antigen (NCA) which was also cross-reactive with CEA. NFA-1 also had a unique determinant not present in CEA or other related antigens including NCA. In a solid-phase RIA system, the reactivity of NFA-1 with a specific anti-CEA antiserum was much stronger than that of NCA. Although digestion with Pronase E did not affect the antigenicity of NFA-1, reduction and alkylation destroyed its antigenic reactivity. The total amount of carbohydrate in NFA-1 was 13.3%, compared to 52.4% in CEA and 21.6% in NCA. The amino acid composition of NFA-1 was similar to that of CEA. The sequence of the first 10 NH2-terminal amino acids in NFA-1 was Ala-Glu-Pro-Pro-Lys-Pro-Phe-Ile-(Thr)-Ser. This was totally different from that of the first NH2-terminal amino acids of CEA isolated from tumor tissue.
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D000941:Antigens / Q000032:analysis / Q000276:immunology*; D002241:Carbohydrates / Q000032:analysis; D002272:Carcinoembryonic Antigen / Q000032:analysis / Q000276:immunology*; D003429:Cross Reactions; D000939:Epitopes / Q000032:analysis; D005243:Feces / Q000032:analysis*; D006801:Humans; D005779:Immunodiffusion; D011402:Pronase / Q000032:analysis; D011817:Rabbits; D011863:Radioimmunoassay
D000596:Amino Acids; D000941:Antigens; D002241:Carbohydrates; D002272:Carcinoembryonic Antigen; D000939:Epitopes; C035221:fecal antigen-1, normal; D011402:Pronase