Open AccessSecondary and quaternary structural transition of the halophilic archaeon nucleoside diphosphate kinase under high‐ and low‐salt conditions
Author(s) -
Ishibashi Matsujiro,
Arakawa Tsutomu,
Philo John S,
Sakashita Kentaro,
Yonezawa Yasushi,
Tokunaga Hiroko,
Tokunaga Masao
Publication year - 2002
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2002.tb11441.x
Subject(s) - random hexamer , halophile , halobacterium salinarum , nucleoside diphosphate kinase , salt (chemistry) , denaturation (fissile materials) , chemistry , dimer , protein quaternary structure , biochemistry , archaea , enzyme , protein subunit , biophysics , biology , organic chemistry , bacteria , nuclear chemistry , genetics , gene
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.