Temperature Dependence of the High-Pressure Denatured State of Lambda Repressor

Abstract

When dropped from 2500 atm to 1 atm in a fast pressure jump experiment, the YG mutant of the five-helix bundle lambda repressor refolds close to the “speed limit”, about 40 times faster than observed in a temperature jump experiment. We carried out molecular dynamics simulations to address the question of why refolding from the pressure denatured state is so much faster than refolding upon temperature jump.The temperature dependence of the high-pressure denatured state of the YG mutant was investigated for this purpose. The high pressure used in the simulation favors denaturation, but also slows down protein dynamics.High temperature was employed to speed up the dynamics. The high-pressure denatured state was identified as a compact structure with the helices I and IV being the most stable elements. Rapid nucleation of helices I and IV may be a major factor in enhancing the refolding rate once the pressure is dropped to 1 atm.