FIG. 1.

Schematic overview of the CVB2O genome organization and the construction of CVB2O variants containing adaptive mutations. (A) A representation of the CVB2O genome is depicted at the top, with boxes delineating viral genes as well as approximate positions of the relevant restriction enzyme sites used to construct infectious viral cDNA clones. Below, the location of amino acid substitutions in the CVB2ORD genome are indicated next to the VP1- and 2C-encoding genes; the first letter refers to the amino acid residue of the CVB2O protein and the number indicates the amino acid position in the individual protein. Infectious CVB2O cDNA clone variants, as inserted in the pCR-Script Direct SK+ vector, are shown in the lower part of the figure. The designation of constructed cDNA clones and simplified names of viruses generated from these clones (given within parentheses) are used throughout the article. (B) A surface-rendered view of a pentameric subunit of the viral capsid showing the location of the exposed CVB2O substitution that evolved during propagation in RD cells. The entire capsid of the closely related CVB3 (PDB 1COV) (58) is shown at the top with five protomers related by an icosahedral 5-fold symmetry axis colored to denote proteins VP1 (blue), VP2 (green), and VP3 (red), whereas the remaining virus surface is shown in shades of gray. Below is an enlarged view of the pentamer showing the location of the surface-exposed amino acid change of CVB2O VP1 (Q164K; cyan and encircled) given as the equivalent CVB3 VP1 residue 160, based on multiple sequence alignment (ClustalW) (79). The icosahedral asymmetric unit of the virus is indicated by the triangular boundary.