The LuxR family quorum-sensing activator MrtR requires its cognate autoinducer for dimerization and activation but not for protein folding.

MrtR, a LuxR homolog in Mesorhizobium tianshanense, is important for symbiosis. We found that MrtR requires its cognate N-acylhomoserine lactone for forming dimers, binding to a single DNA site and activating the downstream promoter. However, MrtR is able to fold independently of its ligand.