In C580Y, we have seen the different scenarios in the RMSD plot, where the large fluctuations are observed for the complete-protein rather than the BTB-domain (Fig. ). The average RMSD value of the complete-protein is 2.55 Å. The probability distribution of RMSD also indicates the broader peak for the complete protein (Fig. ). It reveals that the higher fluctuation in this particular mutant is due to the loss of hydrogen-bond interaction between Cys580-Gly533 residues (Fig. ). No large fluctuations are observed in the R539T and I543T mutants. It has been further revealed that a non-covalent inter-domain hydrogen-interaction between the residue His493 and Glu426 makes the structure more compact (Fig. ). The probability distribution curve indicates that the average value for the interaction is 3.38Å