Regulates the expression of the AceI transporter (PubMed:29481596). Binds DNA and chlorhexidine (PubMed:29481596, PubMed:32636271). Binds to regulatory sites within the intergenic region between the aceI and aceR genes, and affects the interaction between RNA polymerase (RNAP) and promoter DNA both in the presence and in the absence of chlorhexidine (PubMed:29481596, PubMed:32636271). In the absence of chlorhexidine, prevents transcription of the aceI gene by disrupting interactions between the promoter DNA and RNAP (PubMed:32636271). In the presence of chlorhexidine, activates expression of aceI (PubMed:29481596, PubMed:32636271). When AceR interacts with chlorhexidine, it undergoes a conformational change and the tetrameric form either releases the DNA or shifts the position of the DNA-binding region to allow RNAP to bind onto the promoter DNA to proceed with aceI transcription (PubMed:32636271). Homodimer and homotetramer (PubMed:32636271). Binding of chlorhexidine at the inducer-binding domain causes a quaternary structural change that favors interactions between dimers to form tetramers (PubMed:32636271). Binds DNA via its N-terminal domain and the inducer molecule via the C-terminal domain. Deletion mutant shows a decrease in chlorhexidine resistance. Belongs to the LysR transcriptional regulatory family.