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Direct interaction between KaiA and KaiB revealed by a site‐directed spin labeling electron spin resonance analysis
Author(s) -
Mutoh Risa,
Mino Hiroyuki,
Murakami Reiko,
Uzumaki Tatsuya,
Takabayashi Atsushi,
Ishii Kentaro,
Ishiura Masahiro
Publication year - 2010
Publication title -
genes to cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 115
eISSN - 1365-2443
pISSN - 1356-9597
DOI - 10.1111/j.1365-2443.2009.01377.x
Subject(s) - site directed spin labeling , biology , biophysics , residue (chemistry) , biochemistry , chemistry , membrane
In cyanobacteria, three clock proteins, KaiA, KaiB and KaiC, play essential roles in generating circadian oscillations. The interactions of these proteins change during the circadian cycle. Here, we demonstrated direct interaction between KaiA and KaiB using electron spin resonance spectroscopy. We prepared cystein (Cys)‐substituted mutants of Thermosynechococcus elongatus KaiB, labeled specifically their Cys residues with spin labels and measured the ESR spectra of the labeled KaiB. We found that KaiB labeled at the 64th residue showed spectral changes in the presence of KaiA, but not in the presence of KaiC or bovine serum albumin as a negative control. KaiB labeled at the 101st residue showed no such spectral changes even in the presence of KaiA. The results suggest that KaiB interacts with KaiA in the vicinity of the 64th residue of KaiB. Further analysis demonstrated that the C‐terminal clock‐oscillator domain of KaiA is responsible for this interaction.