Koroleva O V, Stepanova E V, Binukov V I, Timofeev V P, Pfeil W
A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, leninsky Prosp., Moscow, Russia.
Biochim Biophys Acta. 2001 Jun 11;1547(2):397-407. doi: 10.1016/s0167-4838(01)00209-6.
The paper reports on two fungal laccases from Coriolus hirsutus and Coriolus zonatus and their type-2 copper-depleted derivatives. Temperature-induced changes of the copper centers were characterized by optical and electron paramagnetic resonance (EPR) spectroscopy, and the overall protein stability by differential scanning microcalorimetry. The intact enzymes showed highly cooperative thermal unfolding transitions at about 90 degrees C. Type-2 copper depletion led to uncoupling of the domains characterized by a different melting pattern which resolved three subtransitions. Melting curves monitored optically at 290, 340 and 610 nm showed additional transitions below thermal unfolding temperature. EPR spectra of the intact laccases showed the disintegration of the trinuclear copper cluster accompanied by loss of one of the copper ions and disappearance of the strong antiferromagnetic coupling in the type-3 site at 70 degrees C and above 70 degrees C. The copper centers of type-2 copper-depleted laccase showed reduced thermotolerance.
