This family contains the bacterial protein YycH which is approximately 450 residues long. YycH plays a role in signal transduction and is found immediately downstream of the essential histidine kinase YycG. YycG forms a two component system together with its cognate response regulator YycF. PhoA fusion studies have shown that YycH is transported across the cytoplasmic protein. It is postulated that YycH functions as an antagonist to YycG. The molecule is made up of three domains, and has a novel three-dimensional structure. The N-terminal domain features a calcium binding site and the central domain contains two conserved loop regions.