The PRV pUL37 R2 region is essential for virulence and can be mutated without causing misfolding of the surrounding protein structure.

<p><b>(A)</b> Kaplan–Meier presentation of mouse survival following intranasal instillation of wild-type PRV (WT) or PRV carrying mutations in the R1, R2, or R3 regions of the pUL37 tegument protein (n = 5 animals for each virus). All viruses encode a mCherry tag fused to the pUL25 capsid protein as previously described [<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1006741#ppat.1006741.ref030" target="_blank">30</a>,<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1006741#ppat.1006741.ref047" target="_blank">47</a>]. <b>(B)</b> The crystal structure of the N-terminal half of the PRV pUL37 R2 mutant (R2; lilac), determined in this work, was overlaid onto the previously determined wild-type structure (WT; beige) [<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1006741#ppat.1006741.ref047" target="_blank">47</a>] with rmsd 0.5538 Å over 479 aligned residues as determined in Coot [<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1006741#ppat.1006741.ref093" target="_blank">93</a>]. A close-up view of R2 is shown to the right with the side chains of the five targeted amino acids indicated for wild type and the mutant.</p>