Article
- The EMBO Journal (1999) 18, 1137 - 1145
- doi:10.1093/emboj/18.5.1137
Physical interactions among circadian clock proteins KaiA, KaiB and KaiC in cyanobacteria
Hideo Iwasaki1, Yasuhito Taniguchi1, Masahiro Ishiura1 and Takao Kondo1
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
Correspondence to:
Takao Kondo, E-mail: kondo@bio.nagoya-u.ac.jp
Masahiro Ishiura, E-mail: ishiura@bio.nagoya-u.ac.jp
Received 24 November 1998; Accepted 7 January 1999; Revised 5 January 1999
Abstract
The kai gene cluster, which is composed of three genes, kaiA, kaiB and kaiC, is essential for the generation of circadian rhythms in the unicellular cyanobacterium Synechococcus sp. strain PCC 7942. Here we demonstrate the direct association of KaiA, KaiB and KaiC in yeast cells using the two-hybrid system, in vitro and in cyanobacterial cells. KaiC enhanced KaiA–KaiB interaction in vitro and in yeast cells, suggesting that the three Kai proteins were able to form a heteromultimeric complex. We also found that a long period mutation kaiA1 dramatically enhanced KaiA–KaiB interaction in vitro. Thus, direct protein–protein association among the Kai proteins may be a critical process in the generation of circadian rhythms in cyanobacteria.
Keywords:
- circadian rhythm,
- kai genes,
- protein–protein interaction,
- Synechococcus
