Highly conserved salt bridge stabilizes a proteinase K subfamily enzyme, Aqualysin I, from Thermus aquaticus YT-1.

ABSTRACT: The proteinase K subfamily enzymes, thermophilic Aqualysin I (AQN) from Thermus aquaticus YT-1 and psychrophilic serine protease (VPR) from Vibrio sp. PA-44, have six and seven salt bridges, respectively. To understand the possible significance of salt bridges in the thermal stability of AQN, we prepared mutant proteins in which amino acid residues participating in salt bridges common to proteinase K subfamily members and intrinsic to AQN were replaced to disrupt the bridges one at a time. Disruption of a salt bridge common to proteinase K subfamily enzymes in the D183N mutant resulted in a significant reduction in thermal stability, and a massive change in the content of the secondary structure was observed, even at 70°C, in the circular dichroism (CD) analysis. These results indicate tha

SUBMITTER: Sakaguchi M 

PROVIDER: S-EPMC4131155 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature