Arginine inhibits Na+-driven flagellar motors of alkaliphilic Bacillus

l-arginine has attracted a great deal of attention as an agent for refolding denatured proteins, and the mildness of its effects offer hope for a wide range of potential applications for this substance, including medicines with few side effects. We report that both l- and d-arginine inhibits Na+-driven flagellar motors of alkaliphilic Bacillus by competing with Na+, which we take as evidence that arginine specifically binds to a molecular target.