Elucidation of the molecular mechanism of heat shock proteins and its correlation with the effects of double mutations S679A & K722Q in the catalytic dyad residues of Lon protease

Abstract Cells can tolerate the effects of temperature shift with the help of small heat shock proteins IbpA and IbpB. The IbpAB protein complex interacts with Lon protease in their free form at physiological temperature to be degraded proteolytically. Lon employs a unique Ser 679 – Lys 722 catalytic dyad to execute the proteolysis of small heat shock proteins. However, the proteolytic degradation of IbpAB is hampered when Lon protease is mutated. The double mutation in the catalytic dyad residues (S679A & K722Q) of Lon brings about some structural changes that affect the proteolytic activity of the mutated Lon protease. However, the detailed molecular aspects of the interactions are not yet fully understood. In the present study, we made an attempt to compare the mode of the interactions between the small heat shock proteins IbpAB with wild type and mutant Lon protease. We for the first time deciphered the molecular details of the mechanism of interaction of small heat shock proteins with the double mutant Lon protease at physiological temperature in absence of proteolytic machinery. Our study may therefore be useful to elucidate the effects of catalytic dyad residue mutations on the mechanism of the proteolytic machinery of mutant Lon protease with IbpA and IbpB.