Figure 4. Structural comparison of zfBG_O and hENG_O.

A. Comparison of the overall structures of zfBG_O and hENG_O, whose strands and helices are shaded orange and blue and green and blue, respectively. Changes in the relative domain orientation of zfBG_O and human ENG_O (green β-strands, cyan helices) is shown in the right most subpanel in which only the backbone atoms of O-D1 have been superposed. B-C. Superposition of zfBG_O and hENG_O O-D1 (B) or O-D2 (C). Distinct orientation of the O-D1 “meander” loop connecting β8-α2 in zfBG_O and β7-α1 in hEng_O is highlighted. Structures are shaded as in panel A, with additional shading of the β8-α2 meander in zfBG_O-D1 and β7-α1 meander in hENG_O-D1 in gold and dark red, respectively. D. Region of super β-sheet formation in the hENG_O:BMP-9 complex, but only with the β-strands corresponding to fingers 3 and 4 (F3 and F4) of BMP-9 shown and the segment of hENG_O extending from β5 to α1 shown. E. Depicts the same as that shown in panel D, but with zfBG_O in place of hENG_O; structure shown was generated by superimposing zfBG_O onto hENG_O in the structure of the hENG_O:BMP-9 complex and then by undisplaying hENG_O. Superposition highlights clashes (red circles) between zfBG_O β8 and finger 4 of BMP-9 for this mode of binding. F. Overlay of the two P2₁2₁2₁ zfBG_O models and one P4₁ zfBG_O model in the region including an additional α-helix (α1) and β-strand (β8) compared to hENG_O. G. 2mFo-DFc electron density for P2₁2₁2₁ zfBG_O (chain A) extending from β6 to α2; map shown was calculated with phenix.maps with a bulk solvent correction and anisotropic scaling and was contoured at 1σ. See also Figures S1, S3, and S8.