Structural Insights into the CRTC2-CREB Complex Assembly on CRE.

The cAMP response element (CRE) binding protein (CREB) is central in the transcription regulation by cAMP, and the CREB-regulated transcriptional coactivators (CRTCs) play critical roles in CREB-mediated transcription activation. Upon stimulation, CRTCs translocate into the nucleus and complex with CREB on CRE promoters to activate target gene transcription. Their physiological importance is underscored by their function in energy balance, long-term memory, longevity and other processes.

Site-directed spin labeling-electron spin resonance mapping of the residues of cyanobacterial clock protein KaiA that are affected by KaiA-KaiC interaction.

The cyanobacterial clock proteins KaiA, KaiB and KaiC interact with each other to generate circadian oscillations. We have identified the residues of the KaiA homodimer affected through association with hexameric KaiC (KaiC6mer) using a spin-label-tagged KaiA C-terminal domain protein (KaiAc) and performing electron spin resonance (ESR) analysis. Cys substitution and/or the attachment of a spin label to residues located at the bottom area of the KaiAc concave surface, a KaiC-binding groove, hindered the association of KaiAc with KaiC6mer, suggesting that the groove likely mediates the interaction with KaiC6mer.

The roles of the dimeric and tetrameric structures of the clock protein KaiB in the generation of circadian oscillations in cyanobacteria.

The molecular machinery of the cyanobacterial circadian clock consists of three proteins, KaiA, KaiB, and KaiC. The three Kai proteins interact with each other and generate circadian oscillations in vitro in the presence of ATP (an in vitro KaiABC clock system). KaiB consists of four subunits organized as a dimer of dimers, and its overall shape is that of an elongated hexagonal plate with a positively charged cleft flanked by two negatively charged ridges.