A timely picture
Niki and Jansen's paper on the structural basis of the day-night switch in the cyanobacterial clock is out in Science this week! This terrifically fun collaboration with Andy LiWang's lab at UC Merced and Susan Golden's lab at UC San Diego began after Andy's lab discovered that one of the Kai clock proteins, KaiB, undergoes a rare metamorphosis to an active, fold-switched state. With Andy's mutations in hand to 'lock' KaiB into its active fold, we were able to capture several high-resolution snapshots of it bound to both KaiC and KaiA, representing the inactive, nighttime complex. Roger Tseng also solved a solution NMR structure of the fold-switched KaiB bound to the output protein CikA. Altogether, these structures and the in vivo work done in the Golden lab demonstrate the unanticipated and essential role that KaiB fold-switching plays in the cyanobacterial circadian clock. Thanks also to Sarvind Tripathi (the crystal whisperer) and Alicia Michael (MALS ninja) for their contributions to the work!