MucR

DNA regions. MucR and its homologs belong to the Ros/MucR family, which is widespread in α-proteobacteria. MucR represents a recent addition to the family of histone-like nucleoid structuring (H-NS) proteins. Despite lacking sequence homology, MucR shares many functional features with H-NS and H-NS-like proteins, including genome structuring and global transcription regulation. In a recent publication (Chaves-Sanjuan et al., 2024), we presented an integrated study combining cryogenic electron microscopy (cryo-EM), nuclear magnetic resonance (NMR), modeling, and biochemical analyses to elucidate the functional architecture of MucR from Brucella abortus and its homolog Ml5 from Mesorhizobium loti. Our results show that MucR and Ml5 form a circular quaternary assembly that enables DNA bridging and condensation through binding to AT-rich sequences. These findings identify Ros/MucR family members as a novel class of H-NS-like proteins and provide a structural model linking nucleoid architecture to transcriptional regulation in α-proteobacteria.