Reactivity of monoclonal antibody A34 in SDS-PAGE immunoblots. (A) The mAb A34 reacts with proteins having apparent molecular weights (lane 1, MW standards) of 61-70 kDa under reducing conditions (lane 2), and 55-67 kDa under non-reducing conditions (lane 3) in detergent lysates from COS cells transfected with an A34 encoding plasmid, but not with detergent lysates from COS cells transfected with an A33 encoding plasmid (lane 4). (B) The mAb A34 reacts with proteins ranging in size from 45-70 kDa (lane 1, MW standards) in detergent lysates of human gastric mucosa (lane 2), but not in detergent lysates of human colonic mucosa (lane 3). Conversely, mAb A33 reacts with a protein having apparent molecular weights of 43 kDa in detergent lysates of human colonic mucosa (lane 4), but not in detergent lysates of human gastric mucosa (lane 5; non-specific reactivity). (C) The mAb A34 reacts with proteins ranging in size from 45-70 kDa (lane 1, MW standards) in human gastric mucosa (lane 2), which upon treatment with N-glycanase PNGaseF, sialidase A, O-glycanase, beta(1-4) Galactosidase, and beta-N-Acetylglucosaminidase (lane 3) are deglycosylated to proteins ranging in size from 33-50 kDa.