Extended Abstract: Structure Determination of Symmetric Protein Complexes by a Complete Search of Symmetry Configuration Space Using NMR Distance Restraints

Symmetric homo-oligomers are protein complexes with similar subunits arranged symmetrically [10]. Figure 1 illustrates the structure of a symmetric homo-oligomer called phospholamban. Phospholamban is a membrane protein that helps regulate the calcium level inside the cell and hence aids in muscle contraction and relaxation [7]; ion conductance studies [5] also suggest that phospholamban might have a separate role as an ion channel. A detailed molecular-level understanding of homo-oligomeric structures provides insights into their functions and, in some cases, how to design appropriate drugs. Nuclear Magnetic Resonance (NMR) spectroscopy underlies many structural studies of homo-oligomers, but poses significant computational challenges in inferring threedimensional structures from indirect (and often sparse) measurements of geometry.