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 可能是关于癌症最好的深度科普（分享） |
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百度了一下，只有毒蛋白，没有毒蛋白质，二者还是有区别的。 -- 哈老怪 - (74 Byte) 2015-1-29 周四, 14:15 (660 reads) |
云飞扬
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作者：云飞扬 在 生活风情 发贴, 来自【海归网】 http://www.haiguinet.com
中文里的区别：
“蛋白”通常是具体的某一种或某一类蛋白质，例如：铬蛋白、血红蛋白、球蛋白等；蛋白质则是所有各种蛋白的总称。
搜索：poisonous protein 或者 toxic protein
疯牛病蛋白：
Major Prion Protein
Remember "Mad Cow Disease," aka bovine spongiform encephalopathy? This is the protein that causes it. Major prion protein (also known as PrP) is already found throughout the human body, particularly within the nervous system. A slight change in the three-dimensional structure of the protein leads to a variety of debilitating and deadly diseases.
蛇毒就是一种混合毒蛋白。
Wiki：https://en.wikipedia.org/wiki/Snake_venom
Venoms contain more than 20 different compounds, mostly proteins and polypeptides.[3] A complex mixture of proteins, enzymes, and various other substances with toxic and lethal properties[2] serves to immobilize the prey animal,[5] enzymes play an important role in the digestion of prey,[4] and various other substances are responsible for important but non-lethal biological effects.[2] Some of the proteins in snake venom have very specific effects on various biological functions including blood coagulation, blood pressure regulation, transmission of the nervous or muscular impulse and have been developed for use as pharmacological or diagnostic tools or even useful drugs.[2]
蛇毒进化：
https://en.wikipedia.org/wiki/Evolution_of_snake_venom
蛇毒基因进化：
ex<x>pression of Venom Gene Homologs in Diverse Python Tissues Suggests a New Model for the Evolution of Snake Venom
https://mbe.oxfordjournals.org/content/early/2014/11/03/molbev.msu294.abstract
基因技术与蛋白毒性：
《Toxic protein cloning and ex<x>pression》
https://www.exptec.com/ex<x>pression%20Technologies/Toxic%20protein%20cloning%20and%20ex<x>pression.htm
Introduction of protein toxicity
Since the beginning of recombinant DNA technology in early 1970s, scientists have found many structural genes or protein-coding cDNAs cannot be readily cloned into a plasmid with a consecutively expressing promoter. With introduction of some regulatory DNA sequences to shut down the consecutive ex<x>pression of the proteins, most structural genes can be cloned and some of them can be expressed. This leads to the development of IPTG induction system. The lac operon is one of the most studied regulatory genes. The lacI repressor binding site is termed lac operator. With introduction of a lac operator after a promoter, lacI repressor will bind on the operator and reduce the non-induced transcription over 90%. This technology leads to the cloning and ex<x>pression of many genes and proteins. It is the most commonly used system in molecular biology studies.
Why a protein is toxic to a host cell?
In a biological system, a particular protein is expressed only in a specific subcellular location, tissue or cell type, during a defined time period, and at a particular quantity level. This is the so called spatial, temporal, and quantitative ex<x>pression. Recombinant protein ex<x>pression often introduces a foreign protein in a host cell and expresses the protein at levels significantly higher than the physiological level of the protein in its native host and at the time the protein is not needed. The over-expressed recombinant protein will perform certain function in the host cell if the protein is expressed soluble and functional. The function of the expressed recombinant protein is often not needed by the host cell. In fact the function of the protein may be detrimental to the proliferation and differentiation of the host cell. The observed phenotypes of the host cells are slow growth rate and low cell density. In some cases, the recombinant protein causes death of the host cell. These phenomena are described as protein toxicity. These recombinant proteins are called toxic proteins.
What percentage of protein is toxic?
Protein toxicity is a commonly observed phenomenon. All active proteins will perform certain functions. All these functions with few exceptions are needed by the host cells and therefore they interfere with cellular proliferation and differentiation. The appeared phenotype of the effects of these proteins to the host cells is their "toxicity". The phenotypes of the protein toxicity are listed bellow. We estimated that about 80% of all soluble proteins have certain degree of toxicity to their hosts. About 10% of all proteins are highly toxic to host cells. The completely insoluble or dysfunctional proteins will not be toxic to the host cell, though they may drain the cellular energy to produce them when over-expressed. Protein over-ex<x>pression creates me<x>tabolic burden for the host cell, but this burden is not toxicity to the cell. Some low solubility or partially functional proteins may still be toxic to the host.
Protein toxicity effects
Protein toxicity adversely affects the cloning and ex<x>pression. For example, the genes or cDNAs of the most toxic proteins are difficult to be cloned. Protein toxicity is the most important reason for DNA cloning or subcloning problems. Most ex<x>pression problems are also the result of protein toxicity. With optimization of ex<x>pression vectors and host cells, we estimate that 80% protein yield problems are the caused by protein toxicity. Only 20% yield problems are the results of other reasons such as codon usage. This is why many codon optimized genes still have ex<x>pression problems.
Are recombinant DNA and RNA toxic to the host cells?
A recombinant DNA fragment is normally not toxic to the host cell unless it contains repetitive sequences which have high affinity to some transcription factors. A functional recombinant RNA can be toxic to the host cells. We estimated that over 80% host toxicity are caused by recombinant proteins, about 15% are caused by recombinant RNA, and less than 1% are caused by recombinant DNA. To reduce or eliminate the toxicity by recombinant RNA, the recombinant RNA transcription should repressed until it is needed. To prevent the toxicity by recombinant DNA, the recombinant DNA fragment should be cloned in the site flanked by some repressors such as the vectors with multiple operators listed bellow. These vectors will bind to repressors to make the DNA fragment inaccessible to the cellular factors and therefore eliminate the toxicity.
作者：云飞扬 在 生活风情 发贴, 来自【海归网】 http://www.haiguinet.com
上一次由云飞扬于2015-1-29 周四, 16:45修改，总共修改了2次
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