Component of a regulatory phosphorelay system that controls B.abortus cell growth, division, and intracellular survival inside mammalian host cells. This signaling pathway is composed of CckA, ChpT, CtrA and CpdR. CtrA is a response regulator substrate of ChpT. When phosphorylated, directly regulates the expression of ccrM. Is also probably involved in the transcriptional regulation of rpoD, pleC, minC and ftsE genes. Forms an asymmetric heterotetramer with ChpT (2:2). There are at least two modes of interaction between ChpT and CtrA, only one of which is competent to catalyze His-Asp phosphoryl transfer. Is phosphorylated by ChpT-P on Asp-51.