H. Lodish - Molecular Cell Biology (5ed, Freeman, 2003) (796244), страница 42
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What do you conclude about the effect of thedrug on the steady-state levels of proteins 1–7?ControlpH4−1104+ DrugpH10−234657++b. You suspect that the drug may be inducing a proteinkinase and so repeat the experiment in part a in the presenceof 32P-labeled inorganic phosphate. In this experiment thetwo-dimensional gels are exposed to x-ray film to detect thepresence of 32P-labeled proteins. The x-ray films are shownbelow.
What do you conclude from this experiment aboutthe effect of the drug on proteins 1–7?4ControlpH104−−+++ DrugpH10c. To determine the cellular localization of proteins 1–7, thecells from part a were separated into nuclear and cytoplasmicfractions by differential centrifugation. Two-dimensional gelswere run and the stained gels are shown below.
What do youconclude about the cellular localization of proteins 1–7?+Control4NuclearpH104−−++CytoplasmicpH10+ Drug4NuclearpH104−−++CytoplasmicpH10Referencesd. Summarize the overall properties of proteins 1–7, combining the data from parts a, b, and c. Describe how youcould determine the identity of any one of the proteins.REFERENCESGeneral ReferencesBerg, J. M., J. L. Tymoczko, and L. Stryer.
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1998. Imposing specificity by localization: Mechanism and evolvability. Curr. Biol. 8:R812–R822.Saibil, H. R., A. L. Horwich, and W. A. Fenton. 2001. Allosteryand protein substrate conformational change during GroEL/GroESmediated protein folding. Adv. Protein Chem. 59:45–72.Yap, K. L., J. A. B. Ames, M. B. Sindells, and M. Ikura. 1999.Diversity of conformational states and changes within the EF-handprotein superfamily. Proteins 37:499–507.Purifying, Detecting, and Characterizing ProteinsHames, B. D. A Practical Approach. Oxford University Press. Amethods series that describes protein purification methods and assays.4BASIC MOLECULARGENETICMECHANISMSElectron micrograph of DNA (green arrow) being transcribed into RNA (red arrow). [O. L.
Miller, Jr., and Barbara R.Beatty, Oak Ridge National Laboratory.]The extraordinary versatility of proteins as molecularmachines and switches, cellular catalysts, and components of cellular structures was described in Chapter3. In this chapter we consider the nucleic acids. These macromolecules (1) contain the information for determining theamino acid sequence and hence the structure and functionof all the proteins of a cell, (2) are part of the cellular structures that select and align amino acids in the correct orderas a polypeptide chain is being synthesized, and (3) catalyzea number of fundamental chemical reactions in cells, including formation of peptide bonds between amino acids duringprotein synthesis.Deoxyribonucleic acid (DNA) contains all the information required to build the cells and tissues of an organism.
The exact replication of this information in anyspecies assures its genetic continuity from generation togeneration and is critical to the normal development of anindividual. The information stored in DNA is arranged inhereditary units, now known as genes, that control identifiable traits of an organism. In the process of transcription, the information stored in DNA is copied into ribonucleic acid (RNA), which has three distinct roles in proteinsynthesis.Messenger RNA (mRNA) carries the instructions fromDNA that specify the correct order of amino acids duringprotein synthesis.
The remarkably accurate, stepwise assembly of amino acids into proteins occurs by translation ofmRNA. In this process, the information in mRNA is interpreted by a second type of RNA called transfer RNA (tRNA)with the aid of a third type of RNA, ribosomal RNA(rRNA), and its associated proteins. As the correct aminoacids are brought into sequence by tRNAs, they are linked bypeptide bonds to make proteins.Discovery of the structure of DNA in 1953 and subsequent elucidation of how DNA directs synthesis of RNA,which then directs assembly of proteins—the so-called centraldogma—were monumental achievements marking the earlydays of molecular biology.
However, the simplified representation of the central dogma as DNAnRNAnprotein doesnot reflect the role of proteins in the synthesis of nucleic acids.Moreover, as discussed in later chapters, proteins are largelyresponsible for regulating gene expression, the entire processwhereby the information encoded in DNA is decoded into theproteins that characterize various cell types.OUTLINE4.1 Structure of Nucleic Acids4.2 Transcription of Protein-Coding Genesand Formation of Functional mRNA4.3 Control of Gene Expression in Prokaryotes4.4 The Three Roles of RNA in Translation4.5 Stepwise Synthesis of Proteins on Ribosomes4.6 DNA Replication4.7 Viruses: Parasites of the Cellular GeneticSystem101102CHAPTER 4 • Basic Molecular Genetic MechanismsDNAvirusdNTPsNucleolus4RNAvirusReplication1 TranscriptionDNArRNArNTPspr e-mRNANucleusCytosol2 RNAprocessingAAAAAmRNARibosomalsubunitsProteinAmino acidsAAAATranslationfactorsAtRNA3 mRNA translation▲ FIGURE 4-1 Overview of four basic molecular geneticprocesses.
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