RESEARCH ARTICLE Structural insights into the architecture and membrane interactions of the conserved COMMD proteins Michael D Healy1, Manuela K Hospenthal2†, Ryan J Hall1, Mintu Chandra1, Molly Chilton3, Vikas Tillu1, Kai-En Chen1, Dion J Celligoi2, Fiona J McDonald4, Peter J Cullen3, J Shaun Lott2, Brett M Collins1*, Rajesh Ghai1* 1Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Australia; 2School of Biological Sciences, The University of Auckland, Auckland, New Zealand; 3School of Biochemistry, Biomedical Sciences Building, University of Bristol, Bristol, United Kingdom; 4Department of Physiology, University of Otago, Dunedin, New Zealand Abstract The COMMD proteins are a conserved family of proteins with central roles in intracellular membrane trafficking and transcription. They form oligomeric complexes with each other and act as components of a larger assembly called the CCC complex, which is localized to endosomal compartments and mediates the transport of several transmembrane cargos. How these complexes are formed however is completely unknown. Here, we have systematically characterised the interactions between human COMMD proteins, and determined structures of *For correspondence:
[email protected] (BMC); COMMD proteins using X-ray crystallography and X-ray scattering to provide insights into the
[email protected] (RG) underlying mechanisms of homo- and heteromeric assembly. All COMMD proteins possess an a- helical N-terminal domain, and a highly conserved C-terminal domain that forms a tightly † Present address: Institute of interlocked dimeric structure responsible for COMMD-COMMD interactions. The COMM domains Structural and Molecular Biology, also bind directly to components of CCC and mediate non-specific membrane association. Overall Department of Biological these studies show that COMMD proteins function as obligatory dimers with conserved domain Sciences, Birkbeck College, London, United Kingdom architectures.