膜蛋白及其分类

这是一篇关于膜蛋白及其分类的思维导图，主要内容有外周/外在膜蛋白、内在/整合膜蛋白、脂描定蛋白。

膜蛋白

• 外周/外在膜蛋白
  • pripheral/extrinsic membrane protein
  • 在细胞膜内（主）外表面
  • 通过离子键、氢键与膜脂分子的极性头部相结合，或通过与内在蛋白的相互作用，间接与膜结合。
• 内在/整合膜蛋白
  • intrinsic/integral membrane protein
  • 不同程度的嵌入脂双层分子中
  • 有的贯穿整个脂双层，两端暴露于膜的内外表面，这种类型的膜蛋白又称跨膜蛋白。
  • singer classification
    • I型
      • 一次跨膜，N端胞外，C端胞内
      • the protein is anchored in the membrane bilayer by a single stretch of about 20 nonionic and predominantly hydrophobic amino acids, almost certainly in an a-helical configuration
      • The hydrophilic domain protruding from the trans face is often very large, constituting the bulk of the polypeptide chain, and contains the NH2 terminus of the chain.
    • II型
      • 一次跨膜，C端胞外，N端胞内
      • Type II proteins are also anchored in the membrane by a single stretch ofpredominantly hydrophobic amino acids, but in this case the hydrophobic stretch is usually near the NH2 terminus ofthe polypeptide chain and is oriented with its NH2 terminus towards the cis face. The bulk of the type II protein is generally contained within the hydrophilic domain situated on the trans side of the membrane, which includes the COOH terminus of the chain.
    • III型
      • 多次跨膜,以4次和7次跨膜多见
      • have multiple hydrophobic stretches of the polypeptide chain embedded in the membrane.
    • IV型
      • 由多个亚单位组成的跨膜通道
      • aggregates of n transmembrane subunits that are identical or closely homologous to one another, with a transmembrane water-filled channel running down the n-fold symmetry or pseudosymmetry axis of the aggregate.
    • V型
      • 多肽链以糖基磷脂酰肌醇(GPI)连接于细胞膜的脂质双层中
    • VI型
      • 一条多肽链的一端以GPI形式连接于胞浆膜,另一端是一次或多次跨膜
• 脂锚定蛋白
  • lipid anchored protein
  • 通过与之共价相连的脂分子插入膜的脂双分子中，从而锚定在细胞质膜上。