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. 2002 May;82(5):2645–2651. doi: 10.1016/S0006-3495(02)75606-3

Studies of Pseudomonas aeruginosa azurin mutants: cavities in beta-barrel do not affect refolding speed.

Irina Pozdnyakova 1, Jesse Guidry 1, Pernilla Wittung-Stafshede 1
PMCID: PMC1302053  PMID: 11964251

Abstract

Pseudomonas aeruginosa azurin is a blue-copper protein with a Greek-key fold. Removal of copper produces an apoprotein with the same structure as holoazurin. To address the effects on thermodynamic stability and folding dynamics caused by small cavities in a beta-barrel, we have studied the behavior of the apo-forms of wild-type and two mutant (His-46-Gly and His-117-Gly) azurins. The equilibrium- and kinetic-folding and unfolding reactions appear as two-state processes for all three proteins. The thermodynamic stability of the two mutants is significantly decreased as compared with the stability of wild-type azurin, in accord with cavities in or near the hydrophobic interior having an overall destabilizing effect. Large differences are also found in the unfolding rates: the mutants unfold much faster than wild-type azurin. In contrast, the folding-rate constants are almost identical for the three proteins and closely match the rate-constant predicted from the native-state topology of azurin. We conclude that the topology is more important than equilibrium stability in determining the folding speed of azurin.

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Selected References

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