This family contains viral TNFR homologs that include vaccinia virus (VACV) cytokine response modifier E (CrmE), an encoded TNFR that shares significant sequence similarity with mammalian type 2 TNF receptors (TNFSFR1B, p75, TNFR type 2), a cowpox virus encoded cytokine-response modifier B (crmB), which is a secreted form of TNF receptor that can contribute to the modification of TNF-mediated antiviral processes, and a myxoma virus (MYXV) T2 (M-T2) protein that binds and inhibits rabbit TNF-alpha. The CrmE structure confirms that the canonical TNFR fold is adopted, but only one of the two "ligand-binding" loops of TNFRSF1A is conserved, suggesting a mechanism for the higher affinity of poxvirus TNFRs for TNFalpha over lymphotoxin-alpha. CrmB protein specifically binds TNF-alpha and TNF-beta indicating that cowpox virus seeks to invade antiviral processes mediated by TNF. Intracellular M-T2 blocks virus-induced lymphocyte apoptosis via a highly conserved viral preligand assembly domain (vPLAD), which controls receptor signaling competency prior to ligand binding.
Jiyao W et al.(2023). "The conserved domain database in 2023.",