Fig. 4. Proposed model of maturation.

(A and F) A cartoon schematic showing several copies of prM-E arranged on a membrane (light blue), illustrating the collapse maturation model for the immature (A) and mature structure (F). Domains are colored as in Fig. 2. (B) The immature trimer of BinJV colored according to symmetry position with prM and E represented as a solid and semitransparent surfaces, respectively. The collapse model involves a refolding of the pr linker, which guides the E ectodomain toward M (see movie S1). (C and H) The transition from immature (C) to mature (H) structure involves minimal displacement of M and a simple collapse of E (see movie S2). Molecules are allowed to migrate from on icosahedral symmetry position to another (see movie S3).Views from the exterior of the virion. Four prM-E are outlined in wedged boxes and displayed as in (B). For the mature structure, subunits are colored according to their original icosahedral symmetry position as defined in (B) and (C). (D) Comparison of a single prM-E subunit between the immature form (left) to the mature form (right). The translation of pr and the ectodomain of E and the rotation of the E stem/TM are indicated. Domains are colored as in Fig. 2. (E) The pr and E components of the trimeric spike are asymmetric in the immature virion (left). By comparison, the spike would follow a pseudo-threefold symmetry if superposed to the M components of the immature spike (right). The arrow represents the twist of the pr and E component of prM-E3 in the actual immature spike. (G) Side view of a dimer of M-E in the mature structure. Mature structures are modeled from DENV-1 in (D), (G), and (H).