The present study describes the biophysical characterization of Arabidopsis thaliana SOG1 (SUPPRESSOR OF GAMMA RESPONSE 1) protein, a NAC domain transcription factor which plays central role in DNA damage response pathway, under salinity stress in vitro. Tryptophan fluorescence studies using purified recombinant wild type (full length) AtSOG1 and its N-terminal or C-terminal deletion forms (AtSOG1 Delta, NAC and AtSOG1 Delta CT respectively) have revealed high salinity induced conformational change due to removal of the N-terminal NAC domain. Bis-ANS binding assays indicate that removal of the N-terminal NAC domain increases the surface hydrophobic binding sites, while the C-terminal region of SOG1 also plays important role in regulating the surface hydrophobicity aspects following exposure to high salinity. Circular dichroism (CD) spectral studies have indicated that removal of the N-terminal NAC domain affects the structural conformation of the protein under high salt concentration. Urea -induced equilibrium unfolding studies revealed decreased stability of C-terminal region due to removal of the N-terminal NAC domain. In vitro aggregation studies have indicated higher propensity of aggregation of AtSOG1 Delta NAC due to salt treatment. Overall, our results provide evidence for the importance of both N-terminal NAC domain and the C-terminal region in regulating the stability of SOG1 protein under salinity stress in vitro. (C) 2019 Elsevier Inc. All rights reserved.