細(xì)胞膜和細(xì)胞表面ppt課件-在線瀏覽
2025-06-21 12:01本頁面
【正文】 部分的主要二級結(jié)構(gòu)是 α螺旋 MembraneEmbedded α Helices Are the Primary Secondary Structures in Most Transmembrane Proteins ? 血型糖蛋白，跨膜螺旋由 2025個疏水性氨基酸構(gòu)成 ? Structure of glycophorin A, a typical singlepass transmembrane protein. Typically, a membraneembedded helix is posed of 20–25 hydrophobic (uncharged) amino acids. The predicted length of such a helix ( nm) is just sufficient to span the hydrocarbon core of a phospholipid bilayer. The hydrophobic side chains protrude outward from the helix and form van der Waals interactions with the fatty acyl chains in the bilayer. ? 七次跨膜螺旋在很多跨膜蛋白中存在，如 G蛋白偶聯(lián)受體， 細(xì)菌中的細(xì)菌視紫質(zhì)。 ? Ion channels pose a second large and important family of multipass transmembrane proteins. As revealed by the crystal structure of a resting K+ channel, ion channels are typically tetrameric proteins. Each of the four subunits has a pair of membranespanning helices that bundle with helices of other subunits, forming a central channel Multiple β Strands in Porins Form embraneSpanning “Barrels ? 革蘭氏陰性細(xì)菌外膜中孔道蛋白，可以小分子親水物質(zhì)進(jìn)出，防止對細(xì)菌有害的進(jìn)入。 ? 離子型去垢劑 (SDS)和非離子型去垢劑（ Triton X100） ? SDS: CH3(CH2)11OSO3Na+ 細(xì)胞膜和細(xì)胞骨架相互影響 Interactions with the Cytoskeleton Impede the Mobility of Integral Membrane Proteins 與蛋白在人工脂質(zhì)體上的表現(xiàn)不同，在活細(xì)胞里，蛋白的移動速率要低的多 1/1030 。 ? 其他參加細(xì)胞粘連的膜蛋白 ? A large number of CAMs fall into four major families: the cadherins, immunoglobulin (Ig) superfamily, integrins, and selectins. ? Some other membrane proteins, whose structures do not belong to any of the major classes of CAMs, also participate in cell–cell adhesion in various tissues. ? 相同粘連分子的連接稱為同親性 homophilic binding，不同粘連分子連接稱為異親性 heterophilic binding ? 細(xì)胞粘連可以是牢固的，如上皮細(xì)胞間的連接；也可以是微弱的，短暫的，如免疫細(xì)胞穿越血管內(nèi)皮。 ? First, CAMs on one cell associate laterally through their extracellular domains or cytosolic domains or both into homodimers or higherorder oligomers in the plane of the cell’s plasma membrane。 these interactions are called intercellular or trans interactions. Trans interactions sometimes induce additional cis interactions and, as a consequence, yet even more trans interactions. 上皮細(xì)胞間的連接和粘連分子 Sheetlike Epithelial Tissues: Junctions and Adhesion Molecules ? 上皮細(xì)胞可分成游離面，基底面和側(cè)面 ? the distinct surfaces of a polarized epithelial cell are called the apical (top), basal (base or bottom), and lateral (side) surfaces 3類連接，錨定，緊密，縫隙 ? 錨定連接對應(yīng)橋粒和中間鏈接，起綁定細(xì)胞作用，緊密連接封閉細(xì)胞間縫隙。 ? Three majo
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