TY - JOUR T1 - A rationally designed c-di-AMP FRET biosensor to monitor nucleotide dynamics JF - bioRxiv DO - 10.1101/2021.02.10.430713 SP - 2021.02.10.430713 AU - Alex J. Pollock AU - Philip H. Choi AU - Shivam A. Zaver AU - Liang Tong AU - Joshua J. Woodward Y1 - 2021/01/01 UR - http://biorxiv.org/content/early/2021/02/11/2021.02.10.430713.abstract N2 - 3’3’-cyclic di-adenosine monophosphate (c-di-AMP) is an important nucleotide second messenger found throughout the bacterial domain of life. C-di-AMP is essential in many bacteria and regulates a diverse array of effector proteins controlling pathogenesis, cell wall homeostasis, osmoregulation, and central metabolism. Despite the ubiquity and importance of c-di-AMP, methods to detect this signaling molecule are limited, particularly at single cell resolution. In this work, crystallization of the Listeria monocytogenes c-di-AMP effector protein Lmo0553 enabled structure guided design of a Förster resonance energy transfer (FRET) based biosensor, which we have named CDA5. CDA5 is a fully genetically encodable, specific, and reversible biosensor which allows for the detection of c-di-AMP dynamics both in vitro and within live single cells in a nondestructive manner. Our initial studies identify a unimodal distribution of c-di-AMP in Bacillus subtilis which decreases rapidly when cells are grown in diluted Luria Broth. Furthermore, we find that B. subtilis mutants lacking either a c-di-AMP phosphodiesterase or cyclase have respectively higher and lower FRET responses, again in a unimodal manner. These findings provide novel insight into c-di-AMP distribution within bacterial populations and establish CDA5 as a powerful platform for characterizing new aspects of c-di-AMP regulation.Importance C-di-AMP is an important nucleotide second messenger for which detection methods are severely limited. In this work we engineer and implement a c-di-AMP specific FRET biosensor to remedy this dearth. We present this biosensor, CDA5, as a versatile tool to investigate previously intractable facets of c-di-AMP biology. ER -