The Mutational Robustness of Influenza A Virus
Mutations were placed onto a structural model of the hemagglutinin protein (PBD 1RVX). Shown are mutations on the head and stem regions, HA1 and HA2. Non-coding mutations (HA-8) and mutations on the signal peptide (HA-11), splice site (HA-1), and transmembrane domain (HA-40, HA-15, HA-10, HA-20) are not shown. Mutations are color coded as follows according to their relative fitness: lethal mutations are red, 0.6–0.8 are orange, 0.8–1.0 are yellow, and 1.0–1.2 are green. We found no HA mutations with a fitness between 0–0.6.