The c-di-AMP-binding protein CbpB modulates the level of ppGpp alarmone in Streptococcus agalactiae.
Covaleda-Cortes, G., Mechaly, A., Brissac, T., Baehre, H., Devaux, L., England, P., Raynal, B., Hoos, S., Gominet, M., Firon, A., Trieu-Cuot, P., Kaminski, P.A.(2023) FEBS J 
- PubMed: 36629470 
- DOI: https://doi.org/10.1111/febs.16724
- Primary Citation of Related Structures:  
6ZZ9 - PubMed Abstract: 
Cyclic di-AMP is an essential signalling molecule in Gram-positive bacteria. This second messenger regulates the osmotic pressure of the cell by interacting directly with the regulatory domains, either RCK_C or CBS domains, of several potassium and osmolyte uptake membrane protein systems. Cyclic di-AMP also targets stand-alone CBS domain proteins such as DarB in Bacillus subtilis and CbpB in Listeria monocytogenes. We show here that the CbpB protein of Group B Streptococcus binds c-di-AMP with a very high affinity. Crystal structures of CbpB reveal the determinants of binding specificity and significant conformational changes occurring upon c-di-AMP binding. Deletion of the cbpB gene alters bacterial growth in low potassium conditions most likely due to a decrease in the amount of ppGpp caused by a loss of interaction between CbpB and Rel, the GTP/GDP pyrophosphokinase.
Organizational Affiliation: 
Unité Biologie des Bactéries Pathogènes à Gram-positif, CNRS UMR 6047, Institut Pasteur, Université Paris Cité, France.