Structural Basis for Type II Membrane Protein Binding by ERM Proteins Revealed by the Radixin-neutral Endopeptidase 24.11 (NEP) Complex*
Structural Basis for Type II Membrane Protein Binding by ERM Proteins Revealed by the Radixin-neutral Endopeptidase 24.11 (NEP) Complex*
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DOI：
10.1074/jbc.m609232200
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发表时间：
2007-07
影响因子：
4.8
通讯作者：
S. Terawaki;K. Kitano;T. Hakoshima
中科院分区：
文献类型：
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作者：
S. Terawaki;K. Kitano;T. Hakoshima
ERM（Ezrin/Radixin/Moesin）蛋白通过同时结合肌动蛋白丝和粘附分子（I型膜蛋白）的C-末端胞质尾来介导膜相关细胞骨架的形成。ERM蛋白还结合中性内肽酶24.11（NEP），一种II型膜蛋白，即使NEP的N-末端胞质尾区具有与I型膜蛋白相反的肽极性。在这里，我们确定了与N-末端NEP胞质肽复合的根蛋白FERM（四点一和ERM）结构域的晶体结构。在FERM-NEP复合物中，肽的两亲性区域形成β链，随后形成发夹，其结合到FERM亚结构域C的浅沟。NEP结合通过β-β相互作用和NEP发夹对接到亚结构域C的疏水口袋中来稳定。然而，NEP在FERM结构域上的结合位点与细胞间粘附分子（ICAM）-2的结合位点重叠，NEP缺乏ICAM-2和相关粘附分子中保守的基序-1序列。NEP发夹虽然缺乏典型的链间氢键，但通过与亚结构域C的主链和侧链的氢键稳定，引导NEP肽的C-末端碱性区域远离凹槽并朝向膜。NEP和Motif-1粘附分子如CD 44的亚结构域C上的结合位点的重叠为通过NEP和ERM蛋白之间的相互作用抑制细胞粘附提供了结构基础。
ERM (Ezrin/Radixin/Moesin) proteins mediate formation of membrane-associated cytoskeletons by simultaneously binding actin filaments and the C-terminal cytoplasmic tails of adhesion molecules (type I membrane proteins). ERM proteins also bind neutral endopeptidase 24.11 (NEP), a type II membrane protein, even though the N-terminal cytoplasmic tail of NEP possesses the opposite peptide polarity to that of type I membrane proteins. Here, we determined the crystal structure of the radixin FERM (Four point one and ERM) domain complexed with the N-terminal NEP cytoplasmic peptide. In the FERM-NEP complex, the amphipathic region of the peptide forms a β strand followed by a hairpin that bind to a shallow groove of FERM subdomain C. NEP binding is stabilized by β-β interactions and docking of the NEP hairpin into the hydrophobic pocket of subdomain C. Whereas the binding site of NEP on the FERM domain overlaps with the binding site of intercellular adhesion molecule (ICAM)-2, NEP lacks the Motif-1 sequence conserved in ICAM-2 and related adhesion molecules. The NEP hairpin, although lacking the typical inter-chain hydrogen bond but is stabilized by hydrogen bonds with the main chain and side chains of subdomain C, directs the C-terminal basic region of the NEP peptide away from the groove and toward the membrane. The overlap of the binding sites on subdomain C for NEP and Motif-1 adhesion molecules such as CD44 provides the structural basis for the suppression of cell adhesion through interaction between NEP and ERM proteins.