Structural basis of the day-night transition in a bacterial circadian clock Tseng, Roger Goularte, Nicolette F. Chavan, Archana Luu, Jansen Cohen, Susan E. Chang, Yong-Gang Heisler, Joel Li, Sheng Michael, Alicia Kathleen Tripathi, Sarvind Golden, Susan S. LiWang, Andy Partch, Carrie L. Multidisciplinary Circadian clocks are ubiquitous timing systems that induce rhythms of biological activities in synchrony with night and day. In cyanobacteria, timing is generated by a posttranslational clock consisting of KaiA, KaiB, and KaiC proteins and a set of output signaling proteins, SasA and CikA, which transduce this rhythm to control gene expression. Here, we describe crystal and nuclear magnetic resonance structures of KaiB-KaiC,KaiA-KaiB-KaiC, and CikA-KaiB complexes. They reveal how the metamorphic properties of KaiB, a protein that adopts two distinct folds, and the post–adenosine triphosphate hydrolysis state of KaiC create a hub around which nighttime signaling events revolve, including inactivation of KaiA and reciprocal regulation of the mutually antagonistic signaling proteins, SasA and CikA. American Association for the Advancement of Science 2017 info:eu-repo/semantics/article doc-type:article text http://purl.org/coar/resource_type/c_2df8fbb1 https://research-explorer.ista.ac.at/record/15156 Tseng R, Goularte NF, Chavan A, et al. Structural basis of the day-night transition in a bacterial circadian clock. <i>Science</i>. 2017;355(6330):1174-1180. doi:<a href="https://doi.org/10.1126/science.aag2516">10.1126/science.aag2516</a> eng info:eu-repo/semantics/altIdentifier/doi/10.1126/science.aag2516 info:eu-repo/semantics/altIdentifier/issn/0036-8075 info:eu-repo/semantics/altIdentifier/e-issn/1095-9203 info:eu-repo/semantics/closedAccess