Effect of α-crystallin on thermal denaturation and aggregation of rabbit muscle glyceraldehyde-3-phosphate dehydrogenase

The study of thermal denaturation of rabbit muscle glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in the presence of α-crystallin by differential scanning calorimetry (DSC) showed that the position of the maximum on the DSC profile (Tmax) was shifted toward lower temperatures with increasing α-crystallin concentration. The diminishing GAPDH stability in the presence of α-crystallin has been explained assuming that heating of GAPDH induces dissociation of the tetrameric form of the enzyme into dimers interacting with α-crystallin. The dissociation of the enzyme tetramer was shown by sedimentation velocity at 45 °C. Suppression of thermal aggregation of GAPDH by α-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 (Rh) plots enabled estimating the hydrodynamic radius of the start aggregates (Rh,0). When aggregation of GAPDH was studied in the presence of α-crystallin, the start aggregates of lesser size were observed.