TABLE 2.

Effects of disulfide bond disruptions in the β3 subunit on αIIbβ3 and αvβ3 expression and activation

ND, not determined.

Domain	Disrupted disulfide bond	αIIbβ3				αvβ3
		Surface expression	Activation state	Induced activation by anti-LIBS6 and Mn2+	Proposed role in αIIbβ3 structure and function	Surface expression	Activation state	Induced activation by anti-LIBS6 and Mn2 +	Proposed role in αvβ3 structure and function
EGF-1	Cys-437-Cys-457	40–50% of WT in all mutants	Profoundly active	Little further activation	Essential for stabilization of the inactive conformer and for the EGF-1 folding	65–85% of WT in all mutants	Moderately active	Further activated	Stabilization of the inactive conformer
EGF-2	Cys-473-Cys-503	∼100% of WT in single mutants. 64% in C473S/C503S	Highly active	Little further activation	Stabilization of the inactive conformer	65–80% of WT in single mutants. 46% in C473S/C503S	Moderately active	Further activated	Stabilization of the inactive conformer
EGF-3	Cys-523-Cys-544	55% of WT in single mutants. 100% in C523S/C544S	Moderately active	Further activated	Stabilization of the inactive conformer	50–60% of WT in single mutants. 100% in C523S/C544S	Single mutants moderately active. C523S/C544S not active	Further activated	Regulatory role for free sulfhydryls in activation
EGF-4	Cys-560-Cys-583	50–70% of WT in all mutants	C560S moderately active, C583S and C560S/C583S almost not active	Further activated	Regulatory role in activation	60–80% of WT in single mutants. 100% in C560/C583S	C560S and C583S slightly active, C560S/C583S not active	Further activated	Regulatory role in activation
	Cys-567-Cys-581	C567S; 20% of WT	ND	ND	Important for the EGF-4 folding	C567S; 32% of WT	ND	ND	Important for the EGF-4 folding
	Cys-575-Cys-586	C575S; 2% of WT	ND	ND	Essential for the EGF-4 folding	C575S; 8% of WT	ND	ND	Essential for the EGF-4 folding