分子生物學(xué)ppt課件(2)-資料下載頁
2025-05-02 12:08本頁面
【正文】 rced into the center of the protein, away from the watery environment of the cell. 51 / 45 Protein Structure and Function Protein chains can fold into plex structures. Proteins can have very different structures and very different functions. 碳酸酐酶 The reaction allows CO2 to dissolve in blood. It can cause this reaction to occur 10,000,000 times faster than normal . active site structure and shape substrate molecules carbonic acid 52 / 45 ?Actin / 肌動蛋白 (a)(b)A n actin monomer? Filaments line inside of cells and are often used to provide support, Actin is a small and simple protein. It can join with other actin to form long and thin actin filament. somewhat like poles holding up a tent. Actin filaments in a cell as seen by flourescence microscopy 53 / 45 ?Kinesin / 驅(qū)動蛋白 Kinesin is used to carry cellular ponents, like anelles, from one end of a cell to another. The cargo is bound to central head region, while the two legs attach to microtubules. As a result, the protein walks along the microtubule toward its destination. microtubule Head region The structure of kinesin includes a pair of legs. 54 / 45 The Dynamics of Proteins ?Proteins are dynamic. This means that their structures are not frozen as fixed shapes. Their structures and even functions can change under different conditions. Actin carbonic anhydrase 55 / 45 ?lockandkey models vs. Inducedfit ?When some enzymes catalyze reactions, their active site changes structure in order to fit well with substrate molecules. This catalysis mechanism is called an inducedfit model(誘導(dǎo)契合機(jī)理 ). ?In some cases catalysis occurs without a change in structure at the active site。 this is called a lockandkey mechanism（鎖鑰機(jī)理） . Substract reaction causes change of active site structure. 56 / 45 ?3?3??? F1 F0 ?ATP synthetase / ATP合成酶 F1： 5種 (9個 )亞基， ?3?3???。α和 β交替排列。 γ 貫穿 αβ復(fù)合體 . 每個 β有一個 ATP合成催化位點(diǎn) F0 ： 3種亞基組成，嵌入內(nèi)膜 12個 c亞基 組成一個環(huán)形結(jié)構(gòu)，具有質(zhì)子通道，可使質(zhì)子由膜間隙流回基質(zhì)。 It has a collection of subunits that spin when the protein is exposed to a gradient of protons. 57 / 45 ?Allosteric regulation / 別構(gòu)調(diào)節(jié) In allosteric regulation, the activity of some proteins can be regulated by the binding of a small molecule to a regulatory site on the protein. 58 / 45 ?lac repressor / lac阻遏蛋白 Because binding of lactose causes a structural change in the DNAbinding domain, which affects protein’ s function. This repressor binds to DNA when lactose binds to regulatory site, it can no longer bind to DNA. Discuss in chapter 3 in detail 59 / 45 Experiments / 實(shí)驗(yàn)研究 The amino acid sequence of a protein is enough to determine its full threedimensional conformation. disrupt interaction among amino acids original structure was restored ?This was demonstrated by a simple experiment known as the ‘ Anfinsen Experiment’ (安芬森實(shí)驗(yàn) ). 蛋白質(zhì)的 多肽鏈 中暗含了形成其空間結(jié)構(gòu)的各種要素，如何折疊盤繞成正確的三維結(jié)構(gòu)是早就注定的。把這種現(xiàn)象稱為一級結(jié)構(gòu)決定高級結(jié)構(gòu)。 60 / 45 Exercises ?How many physical interactions are there involved in protein folding? ?Please describe the threedimensional structures of proteins.
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