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Eukaryotic cells ribosomes

Middlebrook, J. L. and Leatherman D.L. Binding of T-2 toxin to eukaryotic cell ribosomes, Biochem. Pharmacol. 38, 3103, 1989. [Pg.303]

Bacterial protein biosynthesis is a cascade of events which manufacture chains of amino acids before they are folded into specific structures to carry out various biological functions. Protein biosynthesis is absolutely essential for the survival of prokaryotic and eukaryotic cells. Ribosomes, macromolecular complexes made up of proteins and RNA, participate in decoding the genetic message to synthesize both essential and nonessential proteins to carry out cellular functions. [Pg.361]

In contrast, RNA occurs in multiple copies and various forms (Table 11.2). Cells contain up to eight times as much RNA as DNA. RNA has a number of important biological functions, and on this basis, RNA molecules are categorized into several major types messenger RNA, ribosomal RNA, and transfer RNA. Eukaryotic cells contain an additional type, small nuclear RNA (snRNA). With these basic definitions in mind, let s now briefly consider the chemical and structural nature of DNA and the various RNAs. Chapter 12 elaborates on methods to determine the primary structure of nucleic acids by sequencing methods and discusses the secondary and tertiary structures of DNA and RNA. Part rV, Information Transfer, includes a detailed treatment of the dynamic role of nucleic acids in the molecular biology of the cell. [Pg.338]

Ribosomes are ancient ribonucleoprotein complexes that are the sites of protein synthesis in living cells. Their core structures and fundamental functional mechanisms have been conserved throughout the three domains of life bacteria, archaea and eukaryotes. All ribosomes are organized into two subunits that are defined by their apparent sedimentation coefficient, measured in Svedberg units (S). There is a general... [Pg.1085]

Not only eukaryotic cells but also bacteria have successfully been targeted by PNA anhsense strategies. Thus it has been shown that PNA complementary to ribosomal RNA or mRNA encoding an essential fatty acid biosynthesis protein, effectively kills E. coli. Furthermore, it has been shown that PNA directed to the start codon of the y -lactamase gene re-sensitized otherwise resistant E. coli to the antibiohc ampiciUin [64—66]. Conjugating a simple transporter peptide to the PNA increased the potency significantly, and an even more potent antibacterial PNA... [Pg.160]

In addition to the catalytic action served by the snRNAs in the formation of mRNA, several other enzymatic functions have been attributed to RNA. Ribozymes are RNA molecules with catalytic activity. These generally involve transesterification reactions, and most are concerned with RNA metabofism (spfic-ing and endoribonuclease). Recently, a ribosomal RNA component was noted to hydrolyze an aminoacyl ester and thus to play a central role in peptide bond function (peptidyl transferases see Chapter 38). These observations, made in organelles from plants, yeast, viruses, and higher eukaryotic cells, show that RNA can act as an enzyme. This has revolutionized thinking about enzyme action and the origin of life itself. [Pg.356]

Ribosomes in bacteria and in the mitochondria of higher eukaryotic cells differ from the mammalian ribosome described in Ghapter 35. The bacterial ribosome is smaller (70S rather than SOS) and has a different, somewhat simpler complement of RNA and protein... [Pg.371]

Other antibiotics inhibit protein synthesis on all ribosomes (puromycin) or only on those of eukaryotic cells (cycloheximide). Puromycin (Figure 38—11) is a structural analog of tyrosinyl-tRNA. Puromycin is incorporated via the A site on the ribosome into the carboxyl terminal position of a peptide but causes the premature release of the polypeptide. Puromycin, as a tyrosinyl-tRNA analog, effectively inhibits protein synthesis in both prokaryotes and eukaryotes. Cycloheximide inhibits peptidyltransferase in the 60S ribosomal subunit in eukaryotes, presumably by binding to an rRNA component. [Pg.372]

The field of translation initiation has focused on the initial round ofribosomal subunit recruitment to an mRNA. Presumably, these events are mirrored in the subsequent rounds of initiation necessary for polyribosome formation. Importantly, because mRNAs are typically present in large polyribosomes (averaging 9-13 ribosomes per mRNA), the initiation events that govern ribosome recruitment to preexisting polyribosomes constitute the majority of translation initiation cycles occurring in an mRNA s lifetime. Whether or not these initiation events mimic the first round of initiation is not yet known. Since eukaryotic cells divide ribosomes between two subcellular compartments, the cytosol and ER membrane, it is also important to know if the mechanism of translation initiation on ER-bound ribosomes is similar to that occurring on soluble ribosomes and, importantly, whether ER-bound ribosomes can direcdy (re) initiate translation on bound polyribosmes. [Pg.89]

The protein synthesis machinery reads the RNA template starting from the 5 end (the end made first) and makes proteins beginning with the amino terminus. These directionalities are set up so that in prokaryotes, protein synthesis can begin even before the RNA synthesis is complete. Simultaneous transcription-translation can t happen in eukaryotic cells because the nuclear membrane separates the ribosome from the nucleus. [Pg.55]

The answer is b. (Hardman, p 1131.) Chloramphenicol inhibits protein synthesis in bacteria and, to a lesser extent, in eukaryotic cells. The drug binds reversibly to the. 505 ribosomal subunit and prevents attachment of aminoacybtransfer RNA (tRNA) to its binding site. The amino acid substrate is unavailable for peptidyl transferase and peptide bond formation. [Pg.81]

What are the mechanisms by which trichothecenes exert their transcriptional and post-transcriptional effects The 60S ribosomal subunit is a well-known molecular target of trichothecenes in leukocytes and other actively proliferating eukaryotic cells,3 whereas attempts to demonstrate alternative receptors have not been successful.37 38 Translational inhibitors that bind to ribosomes rapidly activate mitogen-activated protein kinases (MAPKs) and apoptosis via a mechanism termed the ribotoxic stress response. 39-40... [Pg.295]

Ered Sanger, a double Nobel Prize winner, sequenced the human mitochondrial genome back in 1981. This genome codes for 13 proteins and the mitochondrion possesses the genetic machinery needed to synthesize them. Thus, the mitochondria are a secondary site for protein synthesis in eukaryotic cells. It turns out that the 13 proteins coded for by the mitochondrial genome and synthesized in the mitochondria are critically important parts of the complexes of the electron transport chain, the site of ATP synthesis. The nuclear DNA codes for the remainder of the mitochondrial proteins and these are synthesized on ribosomes, and subsequently transported to the mitochondria. [Pg.183]

Transcription is catalyzed by DNA-dependent RNA polymerases. These act in a similar way to DNA polymerases (see p. 240), except that they incorporate ribonucleotides instead of deoxyribonucleotides into the newly synthesized strand also, they do not require a primer. Eukaryotic cells contain at least three different types of RNA polymerase. RNA polymerase I synthesizes an RNA with a sedimentation coef cient (see p. 200) of 45 S, which serves as precursor for three ribosomal RNAs. The products of RNA polymerase II are hnRNAs, from which mRNAs later develop, as well as precursors for snRNAs. Finally, RNA polymerase III transcribes genes that code for tRNAs, 5S rRNA, and certain snRNAs. These precursors give rise to functional RNA molecules by a process called RNA maturation (see p. 246). Polymerases II and III are inhibited by a-amanitin, a toxin in the Amanita phalloides mushroom. [Pg.242]

In eukaryotic cells transcription and translation occur in two distinct temporal and spacial events, whereas in prokaryotic cells they occur in one step. As humans have eukaryotic cells, we will look at this process. Transcription occurs on DNA in the nucleus and translation occurs on ribosomes in the cytoplasm. [Pg.336]

The cytoplasmic ribosomes of eukaryotic cells are composed of two subunits. [Pg.170]

Ribosome recycling factor (RRF) and elongation factor-G (EF-G) are required to recycle the prokaryotic ribosome back to a new round of initiation after termination (Nakamura and Ito 2003). No recycling factor has been identified so far in the cytoplasm of eukaryotic cells. To explain this difference it has been postulated that eukaryotic eRF3 has a dual function ... [Pg.5]

Kim SY, Craig EA (2005) Broad sensitivity of Saccharomyces cerevisiae lacking ribosome-associated chaperone Ssb or Zuol to cations, including aminoglycosides. Eukaryot Cell 4 82-89 Kisselev L, Ehrenberg M, Frolova L (2003) Termination of translation interplay of mRNA, rRNAs and release factors . EMBO J 22 175-182... [Pg.25]

Genes can similarly be cloned and expressed in eukaryotic cells, with various species of yeast as the usual hosts. A eukaryotic host can sometimes promote post-translational modifications (changes in protein structure made after synthesis on the ribosomes) that might be required for the function of a cloned eukaryotic protein. [Pg.315]

Posttranscriptional processing is not limited to mRNA. Ribosomal RNAs of both prokaryotic and eukaryotic cells are made from longer precursors called preribosomal RNAs, or pre-rRNAs, synthesized by Pol I. In bacteria, 16S, 23S, and 5S rRNAs (and some tRNAs, although most tRNAs are encoded elsewhere) arise from a single 30S RNA precursor of about 6,500 nucleotides. RNA at both ends of the 30S precursor and segments between the rRNAs are removed during processing (Fig. 26-21). [Pg.1014]

The ribosomes of eukaryotic cells (other than mitochondrial and chloroplast ribosomes) are larger and more complex than bacterial ribosomes (Fig. 27-9d), with a diameter of about 23 nm and a sedimentation coefficient of about 80S. They also have two subunits, which vary in size among species but on average are 60S... [Pg.1048]

In eukaryotic cells, all polypeptides synthesized by cytosolic ribosomes begin with a Met residue (rather than fMet), but, again, the cell uses a specialized initiating... [Pg.1055]

Initiation in Eukaryotic Cells Translation is generally similar in eukaryotic and bacterial cells most of the significant differences are in the mechanism of initiation. Eukaryotic mRNAs are bound to the ribosome as a complex with a number of specific binding proteins. Several of these tie together the 5 and 3 ends of the message. At the 3 end, the mRNA is bound by the poly (A) binding... [Pg.1057]

In bacteria, transcription and translation are tightly coupled. Messenger RNAs are synthesized and translated in the same 5 — 3 direction. Ribosomes begin translating the 5 end of the mRNA before transcription is complete (Fig. 27-28). The situation is quite different in eukaryotic cells, where newly transcribed mRNAs must leave the nucleus before they can be translated. [Pg.1062]

The eukaryotic cell is made up of many structures, compartments, and organelles, each with specific functions that require distinct sets of proteins and enzymes. These proteins (with the exception of those produced in mitochondria and plastids) are synthesized on ribosomes in the cytosol, so how are they directed to their final cellular destinations ... [Pg.1068]

In eukaryotic cells, one class of signal sequences is recognized by the signal recognition particle (SRP), which binds the signal sequence as soon as it appears on the ribosome and transfers the entire ribosome and incomplete polypeptide to the ER. Polypeptides with these signal sequences are moved into the ER lumen as they are synthesized once in the lumen they may be modified and moved to the Golgi complex, then sorted and sent to lysosomes, the plasma membrane, or transport vesicles. [Pg.1077]


See other pages where Eukaryotic cells ribosomes is mentioned: [Pg.149]    [Pg.149]    [Pg.515]    [Pg.345]    [Pg.307]    [Pg.365]    [Pg.391]    [Pg.281]    [Pg.98]    [Pg.220]    [Pg.95]    [Pg.701]    [Pg.183]    [Pg.9]    [Pg.320]    [Pg.484]    [Pg.100]    [Pg.2]    [Pg.23]    [Pg.55]    [Pg.35]    [Pg.1034]    [Pg.1048]    [Pg.1056]   
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