Mechanisms of GII.4 Norovirus Persistence in Human Populations
Figure 1
Evolutionary Analysis of Representative GII.4 Strains from 1987 to Present
Five major evolutionary patterns were observed in the mutational profiles of the GII.4 sequences, and these are represented by GII.4–1987, GII.4–1997, GII.4–2002, GII.4–2004, and GII.4–2005. Yellow, amino acids present in the late 1980s Camberwell cluster (GII.4–1987); red, changes that occurred to form the Grimsby (GII.4–1997) cluster; blue, changes associated with the Farmington Hills (GII.4–2002) cluster; green, changes specific to the Hunter cluster (GII.4–2004); and orange, substitutions important for the Sakai cluster (GII.4–2005). A second GII.4–2002a sequence is included, as it encodes a single amino acid replacement at positively selected position 395 in the P2 subdomain as compared to GII.4–2002. The P2 region is highlighted in dark blue beneath the amino acids, with the N-terminal and C-terminal flanking regions of heterogeneity noted in black for the S domain and brown for P1. Lavender sites represent residues that hydrogen bond to the ligand at site 1; framed residues have been predicted to interact in a second stabilization domain. Amino acids operating under positive selection are marked below the column with a plus sign. Residues that are not colored represent single amino acid changes that were not seen in other strains in the cluster. Strain VA387 is included for comparison, as it is a Grimsby-like virus with a solved crystal structure of the P domain. Bold residues represent amino acids that reverted to a residue from a previous cluster.