H. Lodish - Molecular Cell Biology (5ed, Freeman, 2003) (796244), страница 60
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What is the evidence that the 23S rRNA in the largerRNA subunit has a peptidyl transferase activity?11. How would a mutation in the poly(A)-binding proteinI gene affect translation? How would an electron micrographof polyribosomes from such a mutant differ from the normal pattern?12. What characteristic of DNA results in the requirementthat some DNA synthesis is discontinuous? How areOkazaki fragments and DNA ligase utilized by the cell?13. What gene is unique to retroviruses? Why is the proteinencoded by this gene absolutely necessary for maintainingthe retroviral life cycle, but not that of other viruses?A N A LY Z E T H E DATANASA has identified a new microbe present on Mars and requests that you determine the genetic code of this organism.To accomplish this goal, you isolate an extract from this microbe that contains all the components necessary for proteinsynthesis except mRNA. Synthetic mRNAs are added to thisextract and the resulting polypeptides are analyzed:Synthetic mRNAResulting PolypeptidesAAAAAAAAAAAAAAAALysine-Lysine-Lysine etc.CACACACACACACACAThreonine-HistidineThreonine-Histidine etc.AACAACAACAACAACAThreonine-ThreonineThreonine etc.Glutamine-GlutamineGlutamine etc.Asparagine-AsparagineAsparagine etc.ReferencesFrom these data, what specifics can you conclude about themicrobe’s genetic code? What is the sequence of the anticodonloop of a tRNA carrying a threonine? If you found that thismicrobe contained 61 different tRNAs, what could youspeculate about the fidelity of translation in this organism?REFERENCESStructure of Nucleic AcidsDickerson, R.
E. 1983. The DNA helix and how it is read. Sci.Am. 249:94–111.Doudna, J. A., and T. R. Cech. 2002. The chemical repertoireof natural ribozymes. Nature 418:222–228.Kornberg, A., and T. A. Baker. 1992. DNA Replication, 2d ed.W. H. Freeman and Company, chap. 1. A good summary of the principles of DNA structure.Wang, J. C.
1980. Superhelical DNA. Trends Biochem. Sci.5:219–221.Transcription of Protein-Coding Genes and Formationof Functional mRNABrenner, S., F. Jacob, and M. Meselson. 1961. An unstable intermediate carrying information from genes to ribosomes for proteinsynthesis. Nature 190:576–581.Young, B. A., T. M. Gruber, and C. A.
Gross. 2002. Views oftranscription initiation. Cell 109:417–420.Control of Gene Expression in ProkaryotesBell, C. E., and M. Lewis. 2001. The Lac repressor: a secondgeneration of structural and functional studies. Curr. Opin. Struc.Biol. 11:19–25.Busby, S., and R. H. Ebright. 1999. Transcription activation bycatabolite activator protein (CAP). J. Mol. Biol. 293:199–213.Darst, S. A. 2001. Bacterial RNA polymerase. Curr.
Opin. Struc.Biol. 11:155–162.Muller-Hill, B. 1998. Some repressors of bacterial transcription.Curr. Opin. Microbiol. 1:145–151.The Three Roles of RNA in TranslationAlexander, R. W., and P. Schimmel. 2001. Domain-domain communication in aminoacyl-tRNA synthetases. Prog. Nucleic Acid Res.Mol. Biol. 69:317–349.Bjork, G. R., et al. 1987. Transfer RNA modification. Ann.
Rev.Biochem. 56:263–287.Garrett, R. A., et al., eds. 2000. The Ribosome: Structure, Function, Antibiotics, and Cellular Interactions. ASM Press.Hatfield, D. L., and V. N. Gladyshev. 2002. How selenium hasaltered our understanding of the genetic code.
Mol. Cell Biol.22:3565–3576.Hoagland, M. B., et al. 1958. A soluble ribonucleic acid intermediate in protein synthesis. J. Biol. Chem. 231:241–257.Holley, R. W., et al. 1965. Structure of a ribonucleic acid. Science 147:1462–1465.145Ibba, M., and D. Soll. 2001.The renaissance of aminoacyl-tRNAsynthesis. EMBO Rep. 2:382–387.Khorana, G. H., et al. 1966. Polynucleotide synthesis and thegenetic code. Cold Spring Harbor Symp. Quant. Biol. 31:39–49.Maguire, B.
A., and R. A. Zimmermann. 2001. The ribosomein focus. Cell 104:813–816.Nirenberg, M., et al. 1966. The RNA code in protein synthesis.Cold Spring Harbor Symp. Quant. Biol. 31:11–24.Ramakrishnan, V. 2002. Ribosome structure and the mechanismof translation. Cell 108:557–572.Rich, A., and S.-H. Kim. 1978. The three-dimensional structureof transfer RNA. Sci.
Am. 240(1):52–62 (offprint 1377).Stepwise Synthesis of Proteins on RibosomesGingras, A. C., R. Raught, and N. Sonenberg. 1999. eIF4 initiation factors: effectors of mRNA recruitment to ribosomes and regulators of translation. Ann. Rev. Biochem. 68:913–963.Green, R. 2000. Ribosomal translocation: EF-G turns the crank.Curr. Biol. 10:R369–R373.Hellen, C. U., and P. Sarnow. 2001. Internal ribosome entry sitesin eukaryotic mRNA molecules. Genet. Devel.
15:1593–1612.Kisselev, L. L., and R. H. Buckingham. 2000. Translational termination comes of age. Trends Biochem. Sci. 25:561–566.Kozak, M. 1999. Initiation of translation in prokaryotes andeukaryotes. Gene 234:187–208.Noller, H. F., et al. 2002. Translocation of tRNA during proteinsynthesis. FEBS Lett.
514:11–16.Pestova, T. V., et al. 2001. Molecular mechanisms of translationinitiation in eukaryotes. Proc. Nat’l. Acad. Sci. USA 98:7029–7036.Poole, E., and W. Tate. 2000. Release factors and their role asdecoding proteins: specificity and fidelity for termination of proteinsynthesis. Biochim. Biophys. Acta 1493:1–11.Ramakrishnan, V. 2002. Ribosome structure and the mechanismof translation. Cell 108:557–572.Sonenberg, N., J.
W. B. Hershey, and M. B. Mathews, eds. 2000.Translational Control of Gene Expression. Cold Spring Harbor Laboratory Press.DNA ReplicationBullock, P. A. 1997. The initiation of simian virus 40 DNA replication in vitro. Crit. Rev. Biochem. Mol. Biol. 32:503–568.Kornberg, A., and T. A. Baker. 1992. DNA Replication, 2d ed.W. H. Freeman and CompanyWaga, S., and B. Stillman.
1998. The DNA replication fork ineukaryotic cells. Ann. Rev. Biochem. 67:721–751.Viruses: Parasites of the Cellular Genetic SystemFlint, S. J., et al. 2000. Principles of Virology: Molecular Biology, Pathogenesis, and Control. ASM Press.Hull, R. 2002. Mathews’ Plant Virology. Academic Press.Knipe, D. M., and P. M.
Howley, eds. 2001. Fields Virology. Lippincott Williams & Wilkins.Kornberg, A., and T. A. Baker. 1992. DNA Replication, 2d ed.W. H. Freeman and Company. Good summary of bacteriophagemolecular biology.5BIOMEMBRANESAND CELLARCHITECTUREAtomic force microscopy reveals sphyingomyelin rafts (orange)protruding from a dioleoylphosphatidylcholine background(black) in a mica-supported lipid bilayer.
Placental alkalinephosphatase (yellow peaks), a glycosylphosphatidylinositolanchored protein, is shown to be almost exclusively raftassociated. [From D. E. Saslowsky et al., 2002, J. Biol. Chem.277:26966–26970.]Prokaryotes, which represent the simplest and smallestcells, about 1–2 m in length, are surrounded by aplasma membrane but contain no internal membranelimited subcompartments (see Figure 1-2a). Although DNA isconcentrated in the center of these unicellular organisms, mostenzymes and metabolites are thought to diffuse freely withinthe single internal aqueous compartment. Certain metabolicreactions, including protein synthesis and anaerobic glycolysis,take place there; others, such as the replication of DNA andthe production of ATP, take place at the plasma membrane.In the larger cells of eukaryotes, however, the rates ofchemical reactions would be limited by the diffusion of smallmolecules if a cell were not partitioned into smaller subcompartments termed organelles.
Each organelle is surroundedby one or more biomembranes, and each type of organellecontains a unique complement of proteins—some embeddedin its membrane(s), others in its aqueous interior space, orlumen. These proteins enable each organelle to carry out itscharacteristic cellular functions. The cytoplasm is the partof the cell outside the largest organelle, the nucleus. Thecytosol, the aqueous part of the cytoplasm outside all of theorganelles, also contains its own distinctive proteins.All biomembranes form closed structures, separating thelumen on the inside from the outside, and are based on a similar bilayer structure. They control the movement of molecules between the inside and the outside of a cell and intoand out of the organelles of eukaryotic cells.
In accord withthe importance of internal membranes to cell function, thetotal surface area of these membranes is roughly tenfold asgreat as that of the plasma membrane (Figure 5-1).Although the basic architecture of all eukaryotic cells isconstructed from membranes, organelles, and the cytosol,each type of cell exhibits a distinctive design defined by theshape of the cell and the location of its organelles.
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