Sda mediates the checkpoint control that shuts down sporulation in Bacillus subtilis, and most likely other bacilli, in response to defects in DNA replication and elongation, as well as DNA damage. Sda inhibits the autophosphorylation of KinA, the first kinase in a four-component phosphorelay that culminates in the phosphorylation of SpoOA, a transcription factor that regulates expression of sporulation-specific genes. The structure of Sda does not resemble other kinase inhibitors, and structure-directed mutagenesis, in combination with biochemical and biophysical data, has revealed a novel mechanism of kinase inhibition by Sda.
Rowland SL, Burkholder WF, Cunningham KA, Maciejewski MW, Grossman AD, King GF (2004) Structure and mechanism of action of Sda, an inhibitor of the histidine kinases that regulate initiation of sporulation in Bacillus subtilis. Mol. Cell 13, 689-701.