Effect of Arginine on Chaperone-Like Activity of HspB6 and Monomeric 14-3-3ζ

Abstract

The effect of protein chaperones HspB6 and the monomeric form of the protein 14-3-3ζ (14-3-3ζm) on a test system based on thermal aggregation of UV-irradiated glycogen phosphorylase b (UV-Phb) at 37 °C and a constant ionic strength (0.15 M) was studied using dynamic light scattering. A significant increase in the anti-aggregation activity of HspB6 and 14-3-3ζm was demonstrated in the presence of 0.1 M arginine (Arg). To compare the effects of these chaperones on UV-Phb aggregation, the values of initial stoichiometry of the chaperone–target protein complex (S0) were used. The analysis of the S0 values shows that in the presence of Arg fewer chaperone subunits are needed to completely prevent aggregation of the UV-Phb subunit. The changes in the structures of HspB6 and 14-3-3ζm induced by binding of Arg were evaluated by the fluorescence spectroscopy and differential scanning calorimetry. It was suggested that Arg caused conformational changes in chaperone molecules, which led to a decrease in the thermal stability of protein chaperones and their destabilization.

Effect of Betaine and Arginine on Interaction of αB-Crystallin with Glycogen Phosphorylase b

“…Srinivas [ 28 ] showed that there was little effect of Arg on the secondary or tertiary structure of α-crystallin but that Arg mediated an increase in subunit exchange and destabilization of the α-crystallin structure. In some cases, such destabilization led to an increase in the activity of the chaperone [ 27 , 28 , 29 , 30 ], while in others, as in the case of catalase aggregation at 55 °C, 100 mM Arg decreased the ability of αB-Cr to inhibit aggregation of the target protein [ 29 ].…”

“…To describe the initial part of the stage of protein aggregates growth, the following equation was used [ 30 ]: where, t * is the duration of the nucleation stage, determined by the segment on the abscissa axis, cut off by the theoretical curve calculated from the Equation (2) at I = 0, v 0 is the initial rate of aggregation, and B is a constant.…”

“…In the experiments with chemical chaperones, the same concentration of chaperone was added to both control and sample cells. The correction of the calorimetric traces, analysis of the temperature dependence of excess heat capacity, the thermal stability estimation, and calculation of calorimetric enthalpy (Δ H cal ) was performed as described in [ 30 ].…”

“…Arginine (Arg) regulates the anti-aggregation activity of some sHsps, such as α-crystallin [ 27 , 28 ], HspB5 [ 29 ] or HspB6 [ 30 ], increasing hydrophobic surfaces that results in an increase in the anti-aggregation activity of sHsps. However, sometimes as in case of aggregation of bovine catalase at 55 °C, 0.1 M Arg reduces activity of αB-Cr [ 29 ].…”

Effects of Molecular Crowding and Betaine on HSPB5 Interactions, with Target Proteins Differing in the Quaternary Structure and Aggregation Mechanism

“…Parts of the kinetic curves after the inflection point, corresponding to the initial stage of the aggregate growth, were approximated by the following equation [ 87 ] (as an example, see curve 2, the inset in Figure 1 A): ( I − I 0 ) = v 0 ( t − t *) − B ( t − t *) 2 , t > t * where v 0 is the initial rate of aggregation at the aggregate growth stage, t * is the duration of the lag period of this stage, and B is a constant.…”