ジャーナル: PLoS One / 年: 2011 タイトル: Structural basis for variant-specific neuroligin-binding by α-neurexin. 著者: Hiroki Tanaka / Terukazu Nogi / Norihisa Yasui / Kenji Iwasaki / Junichi Takagi / 要旨: Neurexins (Nrxs) are presynaptic membrane proteins with a single membrane-spanning domain that mediate asymmetric trans-synaptic cell adhesion by binding to their postsynaptic receptor neuroligins. ...Neurexins (Nrxs) are presynaptic membrane proteins with a single membrane-spanning domain that mediate asymmetric trans-synaptic cell adhesion by binding to their postsynaptic receptor neuroligins. α-Nrx has a large extracellular region comprised of multiple copies of laminin, neurexin, sex-hormone-binding globulin (LNS) domains and epidermal growth factor (EGF) modules, while that of β-Nrx has but a single LNS domain. It has long been known that the larger α-Nrx and the shorter β-Nrx show distinct binding behaviors toward different isoforms/variants of neuroligins, although the underlying mechanism has yet to be elucidated. Here, we describe the crystal structure of a fragment corresponding to the C-terminal one-third of the Nrx1α ectodomain, consisting of LNS5-EGF3-LNS6. The 2.3 Å-resolution structure revealed the presence of a domain configuration that was rigidified by inter-domain contacts, as opposed to the more common flexible "beads-on-a-string" arrangement. Although the neuroligin-binding site on the LNS6 domain was completely exposed, the location of the α-Nrx specific LNS5-EGF3 segment proved incompatible with the loop segment inserted in the B+ neuroligin variant, which explains the variant-specific neuroligin recognition capability observed in α-Nrx. This, combined with a low-resolution molecular envelope obtained by a single particle reconstruction performed on negatively stained full-length Nrx1α sample, allowed us to derive a structural model of the α-Nrx ectodomain. This model will help us understand not only how the large α-Nrx ectodomain is accommodated in the synaptic cleft, but also how the trans-synaptic adhesion mediated by α- and β-Nrxs could differentially affect synaptic structure and function.
1. RESIDUE 1068 (UNP RESIDUE NUMBER 1128) WAS A PHE IN THE CDNA USED FOR THIS STUDY; 2. SEQUENCE OF ...1. RESIDUE 1068 (UNP RESIDUE NUMBER 1128) WAS A PHE IN THE CDNA USED FOR THIS STUDY; 2. SEQUENCE OF THE PROTEIN WAS BASED ON ISOFORM 11 OF DATABASE Q28146 (NRX1A_BOVIN).
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実験情報
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実験
実験
手法: X線回折 / 使用した結晶の数: 1
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試料調製
結晶
マシュー密度: 2.52 Å3/Da / 溶媒含有率: 51.22 %
結晶化
温度: 293 K / 手法: 蒸気拡散法, ハンギングドロップ法 / pH: 7 詳細: 18% PEG3000, 0.1M sodium acetate and 0.3M sodium malonate pH 7.0, VAPOR DIFFUSION, HANGING DROP, temperature 293KK