Most halophilic enzymes from extremely halophilic archaea are denatured immediately after transfer from high-salt to low-salt medium. However, nucleoside diphosphate kinase (HsNDK) from the extremely halophilic archaeon Halobacterium salinarum seems to be exceptional, since the enzyme exhibited catalytic activity even under the low-salt condition. Here we show the mechanism how HsNDK is active under both high- and low-salt conditions that the HsNDK hexamer in high-salt medium dissociates into a dimer in the low-salt medium without denaturation. The observed change of the subunit structure was accompanied by a large decrease of α-helical content and lowered thermal sensitivity, yet keeping the conformations. This novel hexamer to dimer conversion under high- and low-salt conditions, respectively, seems to be the mechanism by which HsNDK is avoided from the irreversible denaturation. © 2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.
Ishibashi, M., Arakawa, T., Philo, J. S., Sakashita, K., Yonezawa, Y., Tokunaga, H., & Tokunaga, M. (2002). Secondary and quaternary structural transition of the halophilic archaeon nucleoside diphosphate kinase under high- and low-salt conditions. FEMS Microbiology Letters, 216(2), 235–241. https://doi.org/10.1016/S0378-1097(02)01013-3