Mammalian expression of the IF–Cbl-binding region of wild-type and FM1 mutant cubilin.

(A) The modular protein organization of human cubilin (460 kd) and the IF–Cbl-binding region (cubilin CUB domains 5-8, amino acid 928-1386) expressed in CHO cells stably transfected with miniconstructs of human cubilin cDNA. The region was expressed in 2 variants, the wild-type CUB 5-8 region and the corresponding FM1 mutant form containing the P1297L mutation. (B) Western blotting of the conditioned CHO cell medium containing the 2 analogues of the CUB 5-8 region. The estimated size (approximately 95 kd) of the proteins indicates that glycosylation accounts for approximately 40% of the mass.