Fig. 1: Function and cryo-EM structure of NTCP as HBV receptor.

a, Functional activity assays of rhNTCP. HBV preS1 attachment and HBV infection were evaluated in HepG2 cells expressing rhNTCP by treating the cells with a preS1 probe or HBV in the presence of 3.3 or 10 ng ml rhNTCP, or 500 nM myrcludex B. Percentages indicated the concentration of DDM in the buffer. Cell viability was measured by MTT assay. Data are mean ± s.d. of three independent samples. Scale bar, 100 µm. HBs, HBV surface protein. b, Cryo-EM map contoured with a threshold of 0.020 (left) and ribbon representation (right) of the human NTCP–Fab complex structure. The light and heavy chains of Fab YN69083 are shown in pink and cyan, respectively; NTCP is shown in blue. c, Transmembrane topology diagram of NTCP. The transmembrane helices are grouped by functional domain. Shaded trapezoid regions indicate pseudo-symmetrical regions of the protein. Black dashed lines indicate the position of the membrane bilayer. d, Two orthogonal views of NTCP shown as a Cα ribbon, with helices numbered from the N terminus. Left, the external face is shown at the top. Right, the protein is viewed from outside the cell. e, Comparison of NTCP with the bacterial homologue Y. frederiksenii ASBT. NTCP (blue) is superimposed on Y. frederiksenii ASBT (wheat) (PDB 4N7X), viewed from two perpendicular directions. The additional N-terminal helix of Y. frederiksenii ASBT, which has no equivalent in NTCP, is highlighted in red.