Sequence analysis of carcinoembryonic antigen: identification of glycosylation sites and homology with the immunoglobulin supergene family.
A direct method for the determination of N-linked glycosylation sites in highly glycosylated proteins is described. Carcinoembryonic antigen (CEA) and a nonspecific crossreacting antigen (NCA) were chemically deglycosylated, and peptide maps were prepared by reverse-phase HPLC. The peptides were sequenced on a gas-phase microsequencer, and glycosylation sites were identified as the phenylthiohydantoin derivative of N-acetylglucosaminylasparagine. The sequences were confirmed by fast atom bombardment mass spectrometry. Highly homologous, extended amino-terminal sequences were determined for CEA and two NCAs, NCA-95 and NCA-55. Cysteine-containing sequences for CEA and NCA-95 show up to 95% sequence homology, and the CEA sequences also show internal sequence homologies. A comparison of the CEA sequences with known protein sequences suggests that CEA may be a member of the immunoglobulin supergene family. The protein sequence data have been used to identify a genomic DNA clone for one of the NCA antigens [Thompson, J., Pande, H., Paxton, R. J., Shively, L., Padma, A., Simmer, R. L., Todd, C. W., Riggs, A. D. & Shively, J. E. (1987) Proc. Natl. Acad. Sci. USA, in press] and a cDNA clone for CEA [Zimmermann, W., Ortlieb, B., Friedrich, R. & von Kleist, S. (1987) Proc. Natl. Acad. Sci. USA, in press].
Paxton
R J
RJ
Mooser
G
G
Pande
H
H
Lee
T D
TD
Shively
J E
JE
D000596:Amino Acids / Q000032:analysis; D001483:Base Sequence; D002272:Carcinoembryonic Antigen / Q000235:genetics*; D003545:Cysteine / Q000235:genetics; D006031:Glycosylation; D007136:Immunoglobulins / Q000235:genetics; D010449:Peptide Mapping
D000596:Amino Acids; D002272:Carcinoembryonic Antigen; D007136:Immunoglobulins; D003545:Cysteine