Circadian rhythm

• March 14 1088

• tongli zhang

Circadian rhythm

Circadian rhythms in different organisms

• Control network in mammalian

Circadian rhythms in Cyanobacyteria

cyanobacteria

Their interaction

• KaiA, KaiB and KaiC interact with each other, forming large complexes in vivo.

• KaiC is the core of the complex.

• The complex is mainly at night.

kaiC

KaiA

• kaiA enhances KaiC phosphorylation• KaiA has two domains- N-terminal is a

“pseudo-receive” domain• N-terminal domain of KaiA does not

promote KaiC autophosphorylation• KaiA from anabaena even does not have a

N-terminal domain• However, mutation of N-terminal domain

of KaiA lengthen the circadian period

KaiA 2

• KaiA C-terminal binds KaiC and promotes its phosphorylation

• One KaiA is enough to enhance the phosphotylation of one KaiC hexamer

KaiA 3

• KaiA exists as a domain-swapped homodimer• KaiA's pseudo-receiver domain• The C-terminal domain of KaiA, C-KaiA, is all a-

helical and adopts a novel dimeric structure.

KaiA 4 open and close

• kaiA dimerN of one and C of another interact

• This is closed • When the interaction

is broken- KaiA dimer is open

• Closed is supposed to be the active form

kaiC binding with KaiA

kaiB

• Positively charged residues R23 and K75

kaiC binds with KaiB

• The potentials (positive, blue; negative, red)

A rotary clock

Happy everyone?

• What about

• 1. entrainment?

• 2. temperature compensation?

• 3. fitness?

• 4. cancer development?

Way to solutions.