Circadian clock protein KaiC forms ATP-dependent hexameric rings and binds DNA.
Proc Natl Acad Sci U S A
; 99(26): 17203-8, 2002 Dec 24.
Article
en En
| MEDLINE
| ID: mdl-12477935
ABSTRACT
KaiC from Synechococcus elongatus PCC 7942 (KaiC) is an essential circadian clock protein in cyanobacteria. Previous sequence analyses suggested its inclusion in the RecADnaB superfamily. A characteristic of the proteins of this superfamily is that they form homohexameric complexes that bind DNA. We show here that KaiC also forms ring complexes with a central pore that can be visualized by electron microscopy. A combination of analytical ultracentrifugation and chromatographic analyses demonstrates that these complexes are hexameric. The association of KaiC molecules into hexamers depends on the presence of ATP. The KaiC sequence does not include the obvious DNA-binding motifs found in RecA or DnaB. Nevertheless, KaiC binds forked DNA substrates. These data support the inclusion of KaiC into the RecADnaB superfamily and have important implications for enzymatic activity of KaiC in the circadian clock mechanism that regulates global changes in gene expression patterns.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Proteínas Bacterianas
/
ADN
/
Adenosina Trifosfato
Idioma:
En
Revista:
Proc Natl Acad Sci U S A
Año:
2002
Tipo del documento:
Article
País de afiliación:
Estados Unidos