c-di-AMP recognition by Staphylococcus aureus PstA.

Cyclic-di-AMP (c-di-AMP) is a bacterial secondary messenger involved in various processes, including sensing of DNA-integrity, cell wall metabolism and potassium transport. A number of c-di-AMP receptor proteins have recently been identified in Staphylococcus aureus. One of them - PstA - possesses a ferredoxin-like fold and is structurally related to the class of PII signal-transduction proteins. PII proteins are involved in a large number of pathways, most of them associated with nitrogen metabolism. In this study we describe the mode of c-di-AMP binding and subsequent structural changes of S. aureus PstA. An altered architecture in PstA compared to canonical PII proteins results in differences in ligand coordination.