Table 3.

Distances between EGF molecules and interface parameters in models of possible EGFR oligomers generated from available EGFR crystal structures

EGFR interface	Crystal structure used	Distance between ligands* (Å)	Effect of addition of dye to distance†	Surface area (Å2)‡	ΔG§ (kcal/mol) (p-value)
Back-to-back	1mox (12)	111	Increase	1107	−17.3 (0.043)
Head-to-head	1mox (12)	50	Decrease (min 27 Å)	440	−3.1 (0.430)
Back-to-back	1ivo (13)	111	Increase	1315	−14.0 (0.132)
Weak A:A	1ivo (13)	64	Increase	455	0.3 (0.559)
Weak B:B	1ivo (13)	46	Decrease	284	1.0 (0.749)
Head-to-back§	1nql (15)	53	Similar	956	−9.9 (0.263)
Domain II/IV interactions¶	1nql (15)	68	Similar	655	−5.7 (0.366)
Perpendicular	1yy9 (73)			816	−5.0 (0.417)
HER3 conformation‖	1m6b (64)			1877	−21.0 (0.061)

^*Distances between EGF or TGFα molecules are from the first determined amino acid residues (residues 2/3 in 1mox and residue 5 in 1ivo).

^†Size of Cy3 or Cy5 dye used is ∼20 Å.

^‡Calculated by PISA (53).

^§ΔG is the solvation free energy gain upon formation of the interface, as calculated by PISA. It does not include the effect of satisfied hydrogen bonds and salt bridges across the interface. The p-value is the probability of getting a lower than obtained ΔG, if interface atoms are picked randomly from the protein surface.

^¶Inactive crystallographic dimer.

^‖Crystal of unliganded HER3 dimer.