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The c‐di‐AMP ‐binding protein CbpB modulates the level of ppGpp alarmone in Streptococcus agalactiae

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Covaleda-Cortés, Giovanni | Mechaly, Ariel | Brissac, Terry | Baehre, Heike | Devaux, Laura | England, Patrick | Raynal, Bertrand | Hoos, Sylviane | Gominet, Myriam | Firon, Arnaud | Trieu-Cuot, Patrick | Kaminski, Pierre Alexandre

Edité par CCSD ; Wiley -

International audience. Cyclic di-AMP is an essential signaling 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.

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