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 (PubMed:26124143). When phosphorylated, directly regulates the expression of ccrM (PubMed:10852881). Is also probably involved in the transcriptional regulation of rpoD, pleC, minC and ftsE genes (By similarity). 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, likely on Asp-51. This gene cannot be deleted or disrupted, indicating this gene is essential in B.abortus.