Table 1.

Mutations affecting integrin function

Ligand binding	Activation, integrin		Activation, cellular
	Extracellular	Cytoplasmic
D119N (1)	E312K (2)	R740X (1)	(19)
R214W (2)	G331E (1)	E749K (1)
D217N (14)	S334F (2)	W755X (2)
P219S (1)		P761S (28)
E220K (8)		761 dup (1)
E220Q (1)		Y775X (1)
A252V (1)

On eight separate occasions (EMS-1–EMS-8), cells were treated with EMS and sorted for loss of PAC1 antibody binding. Each EMS experiment yielded multiple different mutations, which have been classed into four major types. Mutant cell lines that failed to restore PAC1 binding upon retransfection with wild-type integrin were classed as cellular mutations. Mutant cell lines that restored PAC1 binding with retransfection were found to have a mutation in the integrin itself. These mutations were found in the ligand binding region, the cytoplasmic domain, or a discrete extracellular region that may be important in the transmission of signal from the cytoplasm to the ligand binding region. Ligand binding mutants were distinguished from activation mutants, as they failed to bind PAC1 in the presence of anti-LIBS6. Although 106 cell lines were isolated, only those fully characterized are shown here. The residue changes of each integrin mutation are listed, followed in parentheses by the number of independent cell lines isolated that have that mutation. In all cases where a mutation was isolated more than once, those isolates were obtained from at least two different EMS experiments. X, truncation at the indicated residue.