GraR (GraR regulator) is a regulatory protein belonging to the two-component signal transduction system, found in Gram-positive bacteria. Together with its sensor kinase GraS, GraR primarily localizes to the cell membrane. This system regulates the expression of antibiotic resistance and virulence genes in bacteria by sensing external stimuli like antibiotics. GraR responds to external signals by altering the transcription of specific genes. Mutations in the gene may affect GraR's functionality, altering bacterial adaptability to environmental stresses.