Structural elucidation of the haptoglobin–hemoglobin clearance mechanism by macrophage scavenger receptor CD163
Fig 2
Cryo-EM structures of the CD163/Hp(1–1)Hb and CD163/HpSPHb complexes.
(A) Cryo-EM map of the CD163/Hp(1–1)Hb complex colored by each component and shown in two side views and one bottom view. A map in transparent representation is contoured at a low level to show electron density for the unresolved flexible domain D1 and unbound HpHb protomer. (B) Molecular model of the CD163/Hp(1–1)Hb complex fitted into the low-contour-level map. (C–D) Representative 2D class averages of CD163/Hp(1–1)Hb (C) and CD163/HpSPHb (D). The protruding unbound HpHb protomer is seen in the 2D class averages of CD163/Hp(1–1)Hb but not in the 2D class averages of CD163/HpSPHb. (E) Cryo-EM map of the CD163/HpSPHb complex colored by each component and shown in two side views and one bottom view. A map in transparent representation is contoured at a low level to show electron density for the flexible peripheral regions. (F) Molecular model of the CD163/HpSPHb complex fitted into the low-contour-level map.