Member of the two-component regulatory system GraR/GraS involved in resistance against cationic antimicrobial peptides (CAMPs). Upon phosphorylation by GraS, functions as a transcription regulator by direct binding to promoter regions of target genes such as adhesins, exoproteins, transporters, toxins, and proteins involved in cell wall synthesis. Down-regulates the expression of many genes involved in RNA and amino acid synthesis or glycolysis. Interacts with GraX. Phosphorylated by GraS. Phosphorylated by Stk1; phosphorylation increases the DNA-binding activity of GraR.