FIG. 3.

The N^ECC region is sufficient for formation of stable heterodimers with N^TMX. (A, B) N^ECC-N^TMX heterodimers were recovered from conditioned media by immunoprecipitation (IP) with either anti-FLAG or anti-HA and were subjected to SDS-PAGE under reducing conditions. Each subunit was then detected by Western blotting for its respective epitope tag. (Top panel) Detection of N^ECC with anti-FLAG; (bottom panel) detection of N^TMX with anti-HA. (A) hN1 heterodimers. (B) hN2 and mN3 heterodimers. The asterisk denotes a polypeptide of slightly smaller molecular weight than hN2 N^ECC that is not competent for association with N^TMX. (C) Sequence alignment of the N^ECC region of various Notch proteins up to the putative furin site (S1). Identical and conserved residues among the sequences are enclosed in black and gray boxes, respectively. H, human; x, Xenopus; m, mouse; r, rat; and zf, zebra fish.