Temperature- and denaturant-induced unfolding of two thermophilic esterases.
We studied the temperature- and denaturant-induced denaturation of two thermophilic esterases, AFEST from Archeoglobus fulgidus and EST2 from Alicyclobacillus acidocaldarius, by means of circular dichroism measurements. Both enzymes showed a very high denaturation temperature: 99 degrees C for AFEST and 91 degrees C for EST2. They also showed a remarkable resistance against urea; at half-completion of the transition the urea concentration was 7.1 M for AFEST and 5.9 M for EST2. On the contrary, both enzymes showed a weak resistance against GuHCl; at half-completion of the transition the GuHCl concentration was 2.0 M for AFEST and 1.9 M for EST2. The thermodynamic parameters characterizing urea- and GuHCl-induced denaturation of the studied enzymes have been obtained by both the linear extrapolation model and the denaturant binding model. The dependence of the thermal stability on NaCl concentration for both esterases has also been determined. A careful analysis of the data, coupled with available structural information, has allowed the proposal of a reliable interpretation.
Del Vecchio
Pompea
P
Department of Chemistry, University of Naples Federico II, Via Cintia, 45-80126 Naples, Italy. delvecchio@chemistry.unina.it
Graziano
Giuseppe
G
Granata
Vincenzo
V
Barone
Guido
G
Mandrich
Luigi
L
Manco
Giuseppe
G
Rossi
Mosè
M
D001407:Bacillus / Q000201:enzymology; D002942:Circular Dichroism; D004795:Enzyme Stability; D004950:Esterases / Q000737:chemistry*; D019791:Guanidine / Q000737:chemistry; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014508:Urea / Q000737:chemistry
D014508:Urea; D004950:Esterases; D019791:Guanidine