Member of at least 2 two-component regulatory systems Hik2/Rre1 and Hik34/Rre1. Responds to hyperosmotic stress, regulates expression of at least 24 genes including dnaK2 and hspA with Hik34 and sigB (sll0306), sll0528, slr1119, slr0852 and ssr3188 with Hik2 (Probable). Responds to salt stress, regulates expression of at least 24 genes including adhA, dnaK2 and hspA with Hik34 (PubMed:15805106, PubMed:19411329). Binds the adhA promoter (PubMed:19411329). Phosphorylated by Hik2 in vitro (PubMed:25714549, PubMed:26904089). Phosphorylated protein has 10-fold higher affinity for DNA than unphosphorylated protein (PubMed:25714549). Interacts with histidine kinase Hik2; may accept phosphate from Hik2. Loss or reduction of expression of about 30 genes in response to hyperosmotic (0.5 M sorbitol) or salt (0.5 M NaCl) stress. Most of these genes encode known heat-shock proteins. Extended N-terminus.