Taxonomic distribution of proteins containing KbaA domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing KbaA domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

Identification of a membrane protein involved in activation of the KinB pathwayto sporulation in Bacillus subtilis.

Dartois V, Djavakhishvili T, Hoch JA
J Bacteriol. 1996; 178: 1178-86

The initiation of sporulation in Bacillus subtilis is dependent on thephosphorylation of the Spo0A transcription factor mediated by the phosphorelayand by two major kinases, KinA and KinB. Temporal expression of these kinases wasanalyzed, and an assessment of their respective contributions to the productionof Spo0A-P was undertaken. The results show that KinB is expressed and activated prior to KinA; i.e., the two kinases are solicited sequentially in thesporulation process and are thought to be activated by different signalingpathways. A strategy was developed to isolate mutations specifically affectingthe KinB pathway, using the newly improved mini-Tn10 delivery vector pIC333.Several mutants were obtained, one of which carried a transposon in a gene codingfor a small integral membrane protein, named KbaA. Inactivation of the kbaA gene appeared to affect KinB activity but not transcription of kinB. A Spo+ suppressor(kinB45) of the kbaA null mutation was isolated in the promoter region of kinB.An eightfold increase of kinB expression levels over wild-type levels wasobserved in the kinB45 mutant. Thus, overexpression of the kinB-kapB operon wassufficient to overcome the sporulation defect caused by inactivation of kbaA in aKinA- strain. Transcription of kinB was found to be repressed by SinR, while the kinB45 mutant was no longer sensitive to SinR regulation. Implications of theseobservations on the transcriptional regulation of kinB and the role of KbaA inKinB activation are discussed.