Fig. 1: ACNDV Cp secondary structure determined by solid-state NMR and alignment of the ACNDV Cp sequence with HBV Cp.

a Secondary chemical shifts of ACNDV Cp at pH 7.5 calculated from assigned CA and CB resonances. Pink background highlights where ≥4 positive secondary chemicals shifts appear in row (α-helix) and blue background where ≥3 negative secondary chemical shifts appear in a row (β-strand). Light blue vertical lines stand for secondary chemical shifts for which only the CA chemical shift was considered either because the residue is a glycine or because the CB chemical shift could not be assigned. Orange lines indicate tentative assignments (Fig. 4) and gray circles represent unassigned residues. Dark pink horizontal bars show α-helices from the cryo-EM structure of ACNDV chain A and gray horizontal lines indicate regions where the map density was not resolved. b The alignment of ACNDV Cp with HBV Cp was taken and adapted from Lauber et al.¹. Annotations for secondary structure elements of ACNDV Cp pH 7.5 chain A are shown above the sequence (DSSP algorithm⁴⁴ in ChimeraX). Gray lines indicate missing residues due to unresolved map density. Helix annotations of HBV Cp chain A of the HBV T = 3 Cp (pdb 6ui6) from²⁹ are shown below the HBV Cp sequence. A small helix, here termed α + as in ACNDV Cp, spans residues 7–9. Note 1.) Our ACNDV plasmid construct used for protein production contained an additional glycine between the first two residues methionine and threonine. Note 2.) The HBV genotype in this adapted Figure is hepatitis B virus genotype D subtype ayw (isolate France/Tiollais/1979) (HBV-D)¹ and the genotype of HBV T = 3 capsids (pdb 6ui6²⁹) used as reference structure throughout this paper is Hepatitis B virus genotype A2 subtype adw (isolate Japan/Nishioka/1983) (HBV-A). Considering residues 1-149, the two protein sequences differ in positions 74 (N/V), 87 (N/S), 97 (I/F), and 116 (L/I). In addition, all cysteines were mutated to alanines in ref. ²⁹ (pdb 6ui6).