How the Virus Outsmarts the Host: Function and Structure of Cytomegalovirus MHC-I-Like Molecules in the Evasion of Natural Killer Cell Surveillance

Table 1

(a) Subunit composition of MHC-I and MHC-I-like viral molecules. (b) Structural differences among MHC-I and MHC-I-like viral molecules.

(a)

Molecule	β2m	Bound peptide ligand
Classical MHC-I (e.g., HLA-A2, H-2D^d)	yes	yes
Viral MHC-I-like molecule
UL18	yes	yes
m144	yes	no
m153	no	no
m157	no	no
2L	no	no

(b)

Molecule	Peptide binding groove	N-terminal extension	H2b helix	Canonical -S-S-		Non-canonical -S-S-
				𝛼1𝛼2 domain; β5→α2	𝛼3 domain; β2→ β6	𝛼1𝛼2 domain	𝛼3 domain
Classical MHC-I; (e.g., HLA-A2, H-2D^d)	yes	no	short	yes	yes	no	no
Viral MHC-I-like
UL18	yes	no	short	yes	yes	no	β4→β5
m144	no	no	short	yes	yes	β2→α1	no
m153	no	Strand, coil	long	no	yes	β4→loop 5	N-term→H2b
m157	no	α0 helix	long	no	yes	Loop 4	β5→β6
2L	no	no	no	no	yes	no	C-term loop