Hsieh, L. Uncovering small RNA-mediated responses to phosphate deficiency in Arabidopsis by deep sequencing. Plant Physiol. Ivanov, P. Angiogenin-induced tRNA fragments inhibit translation initiation. Cell 43, — Jia, J. Cordycedipeptide A, a new cyclodipeptide from the culture liquid of Cordyceps sinensis Berk. Tokyo 53, — Kanoh, K. Antitumor activity of phenylahistin in vitro and in vivo. Kanzaki, H. Enzymatic synthesis of dehydro cyclo His-Phe s, analogs of the potent cell cycle inhibitor, dehydrophenylahistin, and their inhibitory activities toward cell division.
Kaufmann, G. Anticodon nucleases. Trends Biochem. Kawaji, H. Hidden layers of human small RNAs. BMC Genomics Klein, S. Adaptation of Pseudomonas aeruginosa to various conditions includes tRNA-dependent formation of alanyl-phosphatidylglycerol. Kohn, H. The molecular basis for the mode of action of bicyclomycin. Drug Targets. Disord 5, — Krammer, P. Life and death in peripheral T cells. Lautru, S. The albonoursin gene cluster of S noursei biosynthesis of diketopiperazine metabolites independent of nonribosomal peptide synthetases.
Lee, Y. Li, J. Caspases in apoptosis and beyond. Oncogene 27, — Li, Z. Liu, X. Induction of apoptotic program in cell-free extracts: requirement for dATP and cytochrome c. Cell 86, — Lloyd, A. Characterization of tRNA-dependent peptide bond formation by MurM in the synthesis of Streptococcus pneumoniae peptidoglycan.
Lu, P. Translation reinitiation at alternative open reading frames regulates gene expression in an integrated stress response. Magnusson, L. Trends Microbiol. Magyar, A. The antibiotic bicyclomycin affects the secondary RNA binding site of Escherichia coli transcription termination factor Rho. Marquet, R. Biochimie 77, — Marshall, L. Cancer 8, — Marton, M. GCN1, a translational activator of GCN4 in Saccharomyces cerevisiae, is required for phosphorylation of eukaryotic translation initiation factor 2 by protein kinase GCN2.
Pubmed Abstract Pubmed Full Text. Masaki, H. The modes of action of colicins E5 and D, and related cytotoxic tRNases. Biochimie 84, — Maute, R.
Mei, Y. Cell 37, — Minelli, A. Cell Biol. Mogk, A. The N-end rule pathway for regulated proteolysis: prokaryotic and eukaryotic strategies. Trends Cell Biol. Musetti, R. Antifungal activity of diketopiperazines extracted from Alternaria alternata against Plasmopara viticola : an ultrastructural study.
Micron 38, — Nanamiya, H. Identification and functional analysis of novel p ppGpp synthetase genes in Bacillus subtilis.
Nekrasov, M. Nowacka, M. Identification of stable, high copy number, medium-sized RNA degradation intermediates that accumulate in plants under non-stress conditions. Plant Mol. Pavon-Eternod, M. Overexpression of initiator methionine tRNA leads to global reprogramming of tRNA expression and increased proliferation in human epithelial cells.
RNA 19, — Peschel, A. Staphylococcus aureus resistance to human defensins and evasion of neutrophil killing via the novel virulence factor MprF is based on modification of membrane lipids with l-lysine.
Phizicky, E. Do all modifications benefit all tRNAs? Potuschak, T. PRT1 of Arabidopsis thaliana encodes a component of the plant N-end rule pathway. Prasad, C. Bioactive cyclic dipeptides. Peptides 16, — Qiu, H. Rai, R. Identification of mammalian arginyltransferases that modify a specific subset of protein substrates. Riedl, S. Molecular mechanisms of caspase regulation during apoptosis. Rodriguez, P.
Ross, W. The magic spot: a ppGpp binding site on E. Cell 50, — Roy, H. Structural elements defining elongation factor Tu mediated suppression of codon ambiguity. Adaptation of the bacterial membrane to changing environments using aminoacylated phospholipids.
RNA-dependent lipid remodeling by bacterial multiple peptide resistance factors. Broad range amino acid specificity of RNA-dependent lipid remodeling by multiple peptide resistance factors. Royet, J. Peptidoglycan recognition proteins: pleiotropic sensors and effectors of antimicrobial defences. Ruggero, K. Small noncoding RNAs in cells transformed by human T-cell leukemia virus type 1: a role for a tRNA fragment as a primer for reverse transcriptase.
Saad, N. Two-codon T-box riboswitch binding two tRNAs. Saikia, M. Genome-wide identification and quantitative analysis of cleaved tRNA fragments induced by cellular stress. Sanderson, L. RNA 13, — Sattlegger, E. Sauguet, L. Cyclodipeptide synthases, a family of class-I aminoacyl-tRNA synthetase-like enzymes involved in non-ribosomal peptide synthesis. Schaefer, M. Schneider, T. In vitro assembly of a complete, pentaglycine interpeptide bridge containing cell wall precursor lipid II-Gly5 of Staphylococcus aureus.
Shepherd, J. Direction of aminoacylated transfer RNAs into antibiotic synthesis and peptidoglycan-mediated antibiotic resistance. Shrader, T. The N-end rule in Escherichia coli: cloning and analysis of the leucyl, phenylalanyl-tRNA-protein transferase gene aat. Sobala, A. Transfer RNA-derived fragments: origins, processing, and functions.
RNA 2, — Spriggs, K. Translational regulation of gene expression during conditions of cell stress. Cell 40, — Sreedhar, A. Heat shock proteins in the regulation of apoptosis: new strategies in tumor therapy: a comprehensive review.
Staubitz, P. MprF-mediated biosynthesis of lysylphosphatidylglycerol, an important determinant in staphylococcal defensin resistance.
FEMS Microbiol. Strom, K. Suto, K. Sy, J. Tasaki, T. The N-end rule pathway. Thedieck, K. The MprF protein is required for lysinylation of phospholipids in listerial membranes and confers resistance to cationic antimicrobial peptides CAMPs on Listeria monocytogenes.
Thompson, C. Apoptosis in the pathogenesis and treatment of disease. Thompson, D. RNA 14, — Thornberry, N. Caspases: enemies within. Tobias, J. The N-end rule in bacteria. Vattem, K. Vollmer, W. Peptidoglycan structure and architecture. Wang, Q. Wang, X. Nature Cell Biology 6 , doi Each mRNA dictates the order in which amino acids should be added to a growing protein as it is synthesized.
In fact, every amino acid is represented by a three-nucleotide sequence or codon along the mRNA molecule. Figure 7: The ribosome and translation A ribosome is composed of two subunits: large and small.
During translation, ribosomal subunits assemble together like a sandwich on the strand of mRNA, where they proceed to attract tRNA molecules tethered to amino acids circles.
A long chain of amino acids emerges as the ribosome decodes the mRNA sequence into a polypeptide, or a new protein. Each tRNA molecule has two distinct ends, one of which binds to a specific amino acid, and the other which binds to the corresponding mRNA codon. During translation , these tRNAs carry amino acids to the ribosome and join with their complementary codons. Then, the assembled amino acids are joined together as the ribosome, with its resident rRNAs, moves along the mRNA molecule in a ratchet-like motion.
The resulting protein chains can be hundreds of amino acids in length, and synthesizing these molecules requires a huge amount of chemical energy Figure 8. Figure 8: The major steps of translation 1 Translation begins when a ribosome gray docks on a start codon red of an mRNA molecule in the cytoplasm. A second tRNA molecule, bound to two, connected amino acids, is attached to the 4 th , 5 th , and 6 th nucleotide from the left.
It no longer has amino acids bound to its terminus. In step 4, the tRNA molecule that formerly had two connected amino acids attached to its terminus, has now accumulated four amino acids total. Different colored spheres represent different amino acid types, and the four spheres are connected end-to-end in a chain. A tRNA to the right has one amino acid attached to its terminus.
A tRNA molecule carrying a single amino acid is shown approaching the ribosome from the cytoplasm. In step 5, the ribosome is shown to have moved along the length of the mRNA molecule from left to right.
A long chain of approximately 19 amino acids is connected to the end of the tRNA molecule. Five tRNA molecules carrying a single amino acid each are seen floating freely in the cytoplasm surrounding the mRNA molecule. In step 6, the ribosome is disassociated from the mRNA molecule. The amino acid chain has disassociated from the tRNA and is floating freely in the cytoplasm as a complete protein molecule.
The illustrated ribosome is translucent and looks like an upside-down glass jug. The mRNA is composed of many nucleotides that resemble pegs aligned side-by-side along the molecule, in parallel. Each type of nucleotide is represented by a different color yellow, blue, orange, or green. The first three nucleotides, bound to the ribosome, are highlighted in red to represent the stop codon.
In step 2, a tRNA molecule is bound to the stop codon. At the end of the tRNA molecule opposite this point of attachment is an amino acid, represented as a sphere. In step 3, a tRNA bound to a single amino acid is attached to the 7 th , 8 th , and 9 th nucleotide from the left.
In eukaryotic cells, however, the two processes are separated in both space and time: mRNAs are synthesized in the nucleus, and proteins are later made in the cytoplasm.
This page appears in the following eBook. Aa Aa Aa. Ribosomes, Transcription, and Translation. Figure 1: DNA replication of the leading and lagging strand. The helicase unzips the double-stranded DNA for replication, making a forked structure. Figure 3: RNA polymerase at work. What Is the Function of Ribosomes? This Escherichia coli cell has been treated with chemicals and sectioned so its DNA and ribosomes are clearly visible.
Figure 7: The ribosome and translation. A ribosome is composed of two subunits: large and small. Figure 8: The major steps of translation. Cellular DNA contains instructions for building the various proteins the cell needs to survive. In order for a cell to manufacture these proteins, specific genes within its DNA must first be transcribed into molecules of mRNA; then, these transcripts must be translated into chains of amino acids, which later fold into fully functional proteins.
The formation of each peptide bond is catalyzed by peptidyl transferase , an RNA-based ribozyme that is integrated into the 50S ribosomal subunit.
The amino acid bound to the P-site tRNA is also linked to the growing polypeptide chain. Several of the steps during elongation, including binding of a charged aminoacyl tRNA to the A site and translocation, require energy derived from GTP hydrolysis, which is catalyzed by specific elongation factors.
Amazingly, the E. On aligning with the A site, these nonsense codons are recognized by release factors in prokaryotes and eukaryotes that result in the P-site amino acid detaching from its tRNA, releasing the newly made polypeptide. The small and large ribosomal subunits dissociate from the mRNA and from each other; they are recruited almost immediately into another translation init iation complex. In summary, there are several key features that distinguish prokaryotic gene expression from that seen in eukaryotes.
These are illustrated in Figure 6 and listed in Table 1. Figure 6. Post-translational modifications include:. During elongation in translation, to which ribosomal site does an incoming charged tRNA molecule bind?
Which of the following is the amino acid that appears at the N-terminus of all newly translated prokaryotic and eukaryotic polypeptides?
Skip to main content. Mechanisms of Microbial Genetics. Search for:. Protein Synthesis Translation Learning Objectives Describe the genetic code and explain why it is considered almost universal Explain the process of translation and the functions of the molecular machinery of translation Compare translation in eukaryotes and prokaryotes. Think about It How many bases are in each codon?
What amino acid is coded for by the codon AAU? What happens when a stop codon is reached? Think about It Describe the structure and composition of the prokaryotic ribosome. In what direction is the mRNA template read?
Describe the structure and function of a tRNA. Think about It What are the components of the initiation complex for translation in prokaryotes? What are two differences between initiation of prokaryotic and eukaryotic translation? What occurs at each of the three active sites of the ribosome? What causes termination of translation? The genetic code is degenerate in that several mRNA codons code for the same amino acids.
The genetic code is almost universal among living organisms. Prokaryotic 70S and cytoplasmic eukaryotic 80S ribosomes are each composed of a large subunit and a small subunit of differing sizes between the two groups. Each subunit is composed of rRNA and protein. Organelle ribosomes in eukaryotic cells resemble prokaryotic ribosomes. Some 60 to 90 species of tRNA exist in bacteria.
Each tRNA has a three-nucleotide anticodon as well as a binding site for a cognate amino acid. All tRNAs with a specific anticodon will carry the same amino acid. Initiation of translation occurs when the small ribosomal subunit binds with initiation factors and an initiator tRNA at the start codon of an mRNA, followed by the binding to the initiation complex of the large ribosomal subunit. In prokaryotic cells, the start codon codes for N-formyl-methionine carried by a special initiator tRNA.
In eukaryotic cells, the start codon codes for methionine carried by a special initiator tRNA. During the elongation stage of translation, a charged tRNA binds to mRNA in the A site of the ribosome; a peptide bond is catalyzed between the two adjacent amino acids, breaking the bond between the first amino acid and its tRNA; the ribosome moves one codon along the mRNA; and the first tRNA is moved from the P site of the ribosome to the E site and leaves the ribosomal complex.
Termination of translation occurs when the ribosome encounters a stop codon , which does not code for a tRNA. Release factors cause the polypeptide to be released, and the ribosomal complex dissociates.
In prokaryotes, transcription and translation may be coupled, with translation of an mRNA molecule beginning as soon as transcription allows enough mRNA exposure for the binding of a ribosome, prior to transcription termination.
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