Synaptic arrangement of the neuroligin/beta-neurexin complex revealed by X-ray and neutron scattering.
Neuroligins are postsynaptic cell-adhesion proteins that associate with their presynaptic partners, the neurexins. Using small-angle X-ray scattering, we determined the shapes of the extracellular region of several neuroligin isoforms in solution. We conclude that the neuroligins dimerize via the characteristic four-helix bundle observed in cholinesterases, and that the connecting sequence between the globular lobes of the dimer and the cell membrane is elongated, projecting away from the dimer interface. X-ray scattering and neutron contrast variation data show that two neurexin monomers, separated by 107 A, bind at symmetric locations on opposite sides of the long axis of the neuroligin dimer. Using these data, we developed structural models that delineate the spatial arrangements of different neuroligin domains and their partnering molecules. As mutations of neurexin and neuroligin genes appear to be linked to autism, these models provide a structural framework for understanding altered recognition by these proteins in neurodevelopmental disorders.
Comoletti
Davide
D
Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California-San Diego, La Jolla, CA 92093, USA. dcomolet@ucsd.edu
Grishaev
Alexander
A
Whitten
Andrew E
AE
Tsigelny
Igor
I
Taylor
Palmer
P
Trewhella
Jill
J
D000595:Amino Acid Sequence; D000818:Animals; D015816:Cell Adhesion Molecules, Neuronal; D019281:Dimerization; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D033363:Neutron Diffraction; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D053838:Scattering, Small Angle; D012995:Solubility; D013569:Synapses / Q000378:metabolism*; D014961:X-Ray Diffraction
D015816:Cell Adhesion Molecules, Neuronal; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; D011994:Recombinant Proteins; C093438:neuroligin 1