Protein folding at the membrane interface, the structure of Nogo-66 requires interactions with a phosphocholine surface

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 107; no. 15; pp. 6847 - 6851
• Main Authors: Vasudevan, Sheeja V, Schulz, Jessica, Zhou, Chunyi, Cocco, Melanie J
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 13.04.2010; National Acad Sciences
• Subjects: Animals; Axons; Binding sites; Biochemistry; Biological Sciences; Cell Membrane - metabolism; Cell membranes; Cells; Central nervous system; Central Nervous System - metabolism; Dimyristoylphosphatidylcholine - chemistry; Gene expression; GPI-Linked Proteins; Lipids; Magnetic Resonance Spectroscopy - methods; Membrane proteins; Membranes; Mice; Micelles; Models, Molecular; Molecular Conformation; Molecular structure; Myelin Proteins - chemistry; Nervous system; Nogo Receptor 1; Phosphorylcholine - analogs & derivatives; Phosphorylcholine - chemistry; Protein Binding; Protein Folding; Protein Isoforms; Protein Structure, Tertiary; Proteins; Receptors; Receptors, Cell Surface - chemistry; Solvents
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0911817107

Repair of damage to the central nervous system (CNS) is inhibited by the presence of myelin proteins that prevent axonal regrowth. Consequently, growth inhibitors and their common receptor have been identified as targets in the treatment of injury to the CNS. Here we describe the structure of the extracellular domain of the neurite outgrowth inhibitor (Nogo) in a membrane-like environment. Isoforms of Nogo are expressed with a common C terminus containing two transmembrane (TM) helices. The ectodomain between the two TM helices, Nogo-66, is active in preventing axonal growth [GrandPre T, Nakamura F, Vartanian T, Strittmatter SM (2000) Nature 403:439–444]. We studied the structure of Nogo-66 alone and in the presence of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) vesicles and dodecylphosphocholine (DPC) micelles as membrane mimetics. We find that Nogo-66 is largely disordered when free in solution. However, when bound to a phosphocholine surface Nogo-66 adopts a unique, stable fold, even in the absence of TM anchors. Using paramagnetic probes and protein-DPC nuclear Overhauser effects (NOEs), we define portions of the growth inhibitor likely to be accessible on the cell surface. With these data we predict that residues (28-58) are available to bind the Nogo receptor, which is entirely consistent with functional assays. Moreover, the conformations and relative positions of side chains recognized by the receptor are now defined and provide a foundation for antagonist design.