Nonspecific cross-reacting antigen (NCA) expressed by human granulocytes: six species with different peptide sizes and membrane anchoring forms.

We have studied molecular heterogeneity of nonspecific cross-reacting antigen (NCA), a carcinoembryonic antigen (CEA)-related glycoprotein, in human granulocytes. NCAs of 80 and 58 kDa detectable by metabolic labeling (Kuroki, et al., Jpn. J. Cancer Res., 79, 82-90, 1988) were shown to be different molecular species from NCAs of 160, 95, 90 and 26 kDa identified by surface labeling with 125I, suggesting that there exist six different molecular species of NCA in granulocytes. The sizes of the deglycosylated or unglycosylated peptides of the six NCA species of 160, 95, 90, 80, 58 and 26 kDa were approximately 65, 45, 28, 69, 41 and 26 kDa, respectively. Modes of membrane binding of the 95 and 90 kDa NCAs but not of the others were suggested to be of glycosyl-phosphatidylinositol-mediated.