ARHGEF15 and smallpox: The E5 proteins from vaccinia (Western Reserve (WR) strain and Copenhagen strain), variola (the causative agent for smallpox), and cowpox viruses contain an extra 10-amino acid sequence at the N-termini compared with E5 proteins from vaccinia (Ankara), MVA, and ectromelia (mousepox) (Supplementary Fig. 2c).