Table 2 PISA analysis of the four chains in the crystal structure.

From: Crystal structure of caspase-11 CARD provides insights into caspase-11 activation

Structure1 : Structure2

Interface area (Å2)

ΔiG (kcal/mol)

ΔiG P-value

Chain C : Chain B

1058.2

–18.7

0.361

Chain A : Chain D

993.0

–20.2

0.226

Chain A : Chain B

241.0

–5.8

0.296

Chain C : Chain D

224.9

–4.8

0.210

Chain D : Chain B

83.1

–2.7

0.143

Chain A : Chain C

82.1

–2.6

0.093

  1. ΔiG indicates the solvation free energy gain upon formation of the interface, in kcal/mol. Negative ΔiG indicates hydrophobic interfaces or positive protein affinity. This value does not include the effect of the satisfied hydrogen bonds and salt bridges across the interface.
  2. P > 0.5 means that the interface is less hydrophobic than it should be, therefore the interface is likely to be an artifact of crystal packing. P < 0.5 indicates the interface has a higher hydrophobicity than the predicted average for a given structure, implying that the interface surface may be interaction-specific. The limiting case of P = 0 means that no other interface of the observed area may have a lower ΔiG; therefore, this interface is a truly unique spot on the protein surface.
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