The solution structure of ChaB, a putative membrane ion antiporter regulator from Escherichia coli

BACKGROUND: ChaB is a putative regulator of ChaA, a Na(+)/H(+ )antiporter that also has Ca(+)/H(+ )activity in E. coli. ChaB contains a conserved 60-residue region of unknown function found in other bacteria, archaeabacteria and a series of baculoviral proteins. As part of a structural genomics project, the structure of ChaB was elucidated by NMR spectroscopy. RESULTS: The structure of ChaB is composed of 3 α-helices and a small sheet that pack tightly to form a fold that is found in the cyclin-box family of proteins. CONCLUSION: ChaB is distinguished from its putative DNA binding sequence homologues by a highly charged flexible loop region that has weak affinity to Mg(2+ )and Ca(2+ )divalent metal ions.