ABSTRACT
Effects of alpha-crystallin and GroEL on the kinetics of thermal aggregation of rabbit muscle glyceraldehyde-3-phosphate dehydrogenase (GAPDH) have been studied using dynamic light scattering and analytical ultracentrifugation. The analysis of the initial parts of the dependences of the hydrodynamic radius of protein aggregates on time shows that in the presence of alpha-crystallin or GroEL the kinetic regime of GAPDH aggregation is changed from the regime of diffusion-limited cluster-cluster aggregation to the regime of reaction-limited cluster-cluster aggregation, wherein the sticking probability for the colliding particles becomes lower the unity. In contrast to alpha-crystallin, GroEL does not interfere with formation of the start aggregates which include denatured GAPDH molecules. On the basis of the analytical ultracentrifugation data the conclusion has been made that the products of dissociation of GAPDH and alpha-crystallin or GroEL play an important role in the interactions of GAPDH and chaperones at elevated temperatures.
Subject(s)
Escherichia coli Proteins/chemistry , Glyceraldehyde-3-Phosphate Dehydrogenases/chemistry , Heat-Shock Proteins/chemistry , Muscle, Skeletal/enzymology , alpha-Crystallins/chemistry , Animals , Cattle , Kinetics , Male , Muscle, Skeletal/chemistry , Protein Conformation , Rabbits , TemperatureABSTRACT
Effect of alpha-crystallin on thermal inactivation, denaturation and aggregation of aspartate aminotransferase from pig heart mitochondria (mAAT) has been in the focus of this study. Acceleration of heat-induced inactivation of mAAT was demonstrated in the presence of alpha-crystallin. According to the data of differential scanning calorimetry, alpha-crystallin induces destabilization of the mAAT molecule. The size of protein aggregates formed at heating of mAAT at a constant rate (1 degree C/min) has been defined by dynamic light scattering. The obtained data show that aggregation of mAAT in the presence of alpha-crystallin proceeds in the regime of reaction-limited cluster-cluster aggregation.
Subject(s)
Aspartate Aminotransferases/chemistry , Mitochondria/enzymology , Temperature , alpha-Crystallins/pharmacology , Aspartate Aminotransferases/metabolism , Diffusion , Enzyme Activation/drug effects , Enzyme Stability/drug effects , Protein Binding/drug effects , Protein Denaturation/drug effectsABSTRACT
Thermal aggregation of aspartate aminotransferase from pig heart mitochondria (mAAT) has been studied at various temperatures and various protein concentrations by dynamic light scattering. The character of the dependence of protein aggregate size on time indicates that aggregation of mAAT proceeds in the regime of diffusion-limited cluster-cluster aggregation. Suppression of mAAT aggregation by alpha-crystallin is due to transition of the aggregation process into the regime of reaction-limited cluster-cluster aggregation. Realization of this regime of aggregation means that the sticking probability for the colliding particles is less than unity.
Subject(s)
Aspartate Aminotransferase, Mitochondrial/chemistry , Aspartate Aminotransferase, Mitochondrial/metabolism , Temperature , alpha-Crystallins/pharmacology , Animals , Cattle , Kinetics , Light , Protein Binding/drug effects , Scattering, RadiationABSTRACT
Kinetics of thermal aggregation of yeast alcohol dehydrogenase I (yADH) have been studied using dynamic light scattering at a fixed temperature (56 degrees C) and under the conditions where the temperature was elevated at a constant rate (1 K/min). The initial parts of the dependences of the hydrodynamic radius on time (or temperature) follow the exponential law. At rather high values of time splitting of the population of aggregates into two components occurs. It is assumed that such peculiarities of the kinetics of thermal aggregation of yADH are due to the presence of a sequence -YSGVCHTDLHAWHGDWPLPVK- in the polypeptide chain possessing chaperone-like activity. Thermodynamic parameters for thermal denaturation of yADH have been calculated from the differential scanning calorimetry data.
Subject(s)
Alcohol Dehydrogenase/chemistry , Saccharomyces cerevisiae/enzymology , Alcohol Dehydrogenase/genetics , Alcohol Dehydrogenase/metabolism , Amino Acid Sequence , Animals , Cattle , Hot Temperature , Light , Models, Molecular , Molecular Chaperones/chemistry , Molecular Chaperones/genetics , Molecular Chaperones/metabolism , Molecular Sequence Data , Multiprotein Complexes , Protein Denaturation , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae Proteins/chemistry , Saccharomyces cerevisiae Proteins/genetics , Saccharomyces cerevisiae Proteins/metabolism , Scattering, Radiation , Thermodynamics , Ultraviolet Rays , beta-Crystallins/chemistry , beta-Crystallins/radiation effectsABSTRACT
A comparative study of thermal denaturation and inactivation of aspartate aminotransferase from pig heart mitochondria (mAAT) has been carried out (10 mM Na phosphate buffer, pH 7.5). Analysis of the data on differential scanning calorimetry shows that thermal denaturation of mAAT follows the kinetics of irreversible reaction of the first order. The kinetics of thermal inactivation of mAAT follows the exponential law. It has been shown that the inactivation rate constant (k(in)) is higher than the denaturation rate constant (k(den)). The k(in)/k(den) ratio decreases from 28.8+/-0.1 to 1.30+/-0.09 as the temperature increases from 57.5 to 77 degrees C. The kinetic model explaining the discrepancy between the inactivation and denaturation rates has been proposed. The size of the protein aggregates formed at heating of mAAT at a constant rate (1 degrees C min(- 1)) has been characterized by dynamic light scattering.
Subject(s)
Aspartate Aminotransferase, Mitochondrial/chemistry , Temperature , Animals , Calorimetry, Differential Scanning , Light , Mitochondria, Heart/enzymology , Protein Binding , Protein Denaturation , Scattering, Radiation , SwineABSTRACT
The study of thermal denaturation of rabbit muscle glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in the presence of alpha-crystallin by differential scanning calorimetry (DSC) showed that the position of the maximum on the DSC profile (T(max)) was shifted toward lower temperatures with increasing alpha-crystallin concentration. The diminishing GAPDH stability in the presence of alpha-crystallin has been explained assuming that heating of GAPDH induces dissociation of the tetrameric form of the enzyme into dimers interacting with alpha-crystallin. The dissociation of the enzyme tetramer was shown by sedimentation velocity at 45 degrees C. Suppression of thermal aggregation of GAPDH by alpha-crystallin was studied by dynamic light scattering under the conditions wherein temperature was elevated at a constant rate. The construction of the light scattering intensity versus the hydrodynamic radius (R(h)) plots enabled estimating the hydrodynamic radius of the start aggregates (R(h,0)). When aggregation of GAPDH was studied in the presence of alpha-crystallin, the start aggregates of lesser size were observed.
