Reduction of salt-requirement of halophilic nucleoside diphosphate kinase by engineering S-S bond

Ishibashi, Matsujiro*; Uchino, Manami*; Arai, Shigeki; Kuroki, Ryota; Arakawa, Tsutomu*; Tokunaga, Masao*

Archives of Biochemistry and Biophysics, 525(1), p.47 - 52, 2012/09

https://doi.org/10.1016/j.abb.2012.05.021

Nucleoside diphosphate kinase (HsNDK) from Halobacterium salinarum requires salt at high concentrations for folding. A D148C mutant, in which Asp148 was replaced with Cys, was designed to enhance stability and folding in low salt solution by S-S bond. It showed increased thermal stability by about 10C in 0.2 M NaCl over the wild type HsNDK. It refolded from heat-denaturation even in 0.1 M NaCl, while the wild type required 2 M NaCl to achieve the same level of activity recovery. This enhanced refolding is due to the three S-S bonds between two basic dimeric units in the hexameric HsNDK structure. Moreover, salt concentration dependency of heat-denaturation process and refolding process of the wild type and D148C mutant HsNDKs were investigated by the circular dichroism and native-PAGE analysis.