Figure 2.

Structure of the PCSK9/LDLR complex. Colour scheme: PCSK9 prodomain (Pro, blue), catalytic (Cat, red) and C-terminal (CTD, brown) domains; LDLR domains are L7 (beige), EGF(A) (yellow), EGF(B) (green) and β-propeller/EGF(C) (cyan). Spheres indicate Ca²⁺ ions. PCSK9 residues 212–222 form a disordered loop (red dashes) harbouring the furin cleavage site (RFHR₂₁₈). Box: details of the β-propeller/prodomain interface; side-chain sticks for S127, D129, R385, N404 and N407 show the close proximity of residues associated with familial hypercholesterolaemia; side-chain labels are colour coded: PCSK9, red; LDLR, grey. CTD, C-terminal histidine-rich domain; EGF, epidermal growth factor; LDLR, low-density lipoprotein receptor; PCSK9, proprotein convertase subtilisin/kexin type 9.