Fig. 6: The Lin12-Notch repeat (LNR) modules of the PAPP-A subunit.

a Cartoon representation of PAPP-A LNR1 (green) and the C domain (light blue), including LNR3 (dark green). LNR1 and LNR3 are superimposed. Disulfide bonds (yellow) and the position of the two Ca2+ ions (spheres) are shown. b Sequence alignment of the three PAPP-A LNR modules emphasizing coordinating residues (highlighted in green). LNR1 has two disulfide bonds. LNR2 has one disulfide bond and an unpaired cysteine (C461, marked yellow). LNR3 has two disulfide bonds arranged in the 1-3/2-4 pattern of LNR1, but two of the cysteine residues are not aligned. c Maps around the Ca2+ ions of LNR1 and LNR3, respectively. The map (MAP1) was contoured at 4.0 σ.