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 ( T max) 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 ( 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 α-crystallin, the start aggregates of lesser size were observed.