作业帮有谁知道Ⅰ型跨膜蛋白和Ⅱ型跨膜蛋白的定义和区别?
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有谁知道Ⅰ型跨膜蛋白和Ⅱ型跨膜蛋白的定义和区别?
有谁知道Ⅰ型跨膜蛋白和Ⅱ型跨膜蛋白的定义和区别?
有谁知道Ⅰ型跨膜蛋白和Ⅱ型跨膜蛋白的定义和区别?
膜蛋白 生物膜所含的蛋白叫膜蛋白,是生物膜功能的主要承担者.
根据蛋白分离的难易及在膜中分布的位置,膜蛋白基本可分为两大类：外在膜蛋白和内在膜蛋白.外在膜蛋白约占膜蛋白的20％～30％,分布在膜的内外表面,主要在内表面,为水溶性蛋白,它通过离子键、；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；内在蛋白约占膜蛋白的70％～80％,是双亲媒性分子,可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.内在膜蛋白露出膜外的部分含较多的极性氨基酸,属亲水性,与磷脂分子的亲水头部邻近；嵌入脂双层内部的膜蛋白由一些非极性的氨基酸组成,与脂质分子的疏水尾部相互结合,因此与膜结合非常紧密.
Types I, II, and III are single pass molecules, while type IV are multiple pass molecules. Type I transmembrane proteins are anchored to the lipid membrane with a stop-transfer anchor sequence and hav...
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Types I, II, and III are single pass molecules, while type IV are multiple pass molecules. Type I transmembrane proteins are anchored to the lipid membrane with a stop-transfer anchor sequence and have their N-terminal domains targeted to the ER lumen during synthesis (and the extracellular space, if mature forms are located on plasmalemma). Type II and III are anchored with a signal-anchor sequence, with type II being targeted to the ER lumen with its C-terminal domain, while type III have their N-terminal domains targeted to the ER lumen. Type IV is subdivided into IV-A, with their N-terminal domains targeted to the cytosol and IV-B, with an N-terminal domain targeted to the lumen.[5] The implications for the division in the four types are especially manifest at the time of translocation and ER-bound translation, when the protein has to be passed through the ER membrane in a direction dependent on the type.
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