1.3. Elongation cycle
The elongation cycle is highly conserved across all kingdoms of life. Each cycle of elongation adds one amino acid to the C-terminus of the newly synthesized peptide (Yu et al., 2014). Figure 9 describes the steps involved in the elongation cycle. Figure 9. Bacterial elongation cycle. Elongation cycle involves sequential addition of amino acid to the growing peptide chain. Aminoacylated tRNA in complex with EF-Tu and GTP interacts with the A-site in the decoding center where the correctness of the codon-anticodon is determined. On accommodation aa-tRNA moves into the PTC after which the ribosome forms the hybrid A/P and P/E state in preparation of translocation. After GTP hydrolysis, dissociation of E-F-Tu-GDP and translocation, new aa-tRNA ternary complex reads the codon on the mRNA and continues this cycle(Voorhees e Ramakrishnan, 2013)
Aminoacylation and Delivery of aa-tRNA to the A-site:
E.coli has 20 amino acids, 20 aminoacyl
In this step, large ribosomal subunit protein L7/L12 stalk (L7 differs from L12 by an acetylated N terminus) interacts with helix D of EF-Tu, using its flexible C-terminal domain and delivers the ternary complex to the A-site of the ribosome, shown in figure 11. The stalk is made of two L7/L12 dimers. The N-terminal domain aids in formation of the dimer and anchoring the protein to the ribosomes whereas the C-terminal domain binds to EF-Tu in the ternary complex (Savelsbergh et al., 2000). Figure 11. L7/L12 stalk. The 50S subunit rRNA is depicted in gray and the 50S r-proteins are shown in cyan. The L12 dimers are shown in red with its CTD, NTD and the hinge region. The L10 that provides flexibility is shown in blue while the L11 acting as a anchor is shown in yellow. The L7/L12 dimer stalk aids in delivery of the aa-tRNA ternary complex to the A-site of the ribosome (Diaconu et al.,
Once the recombinant plasmid was obtained, it was then inserted into E. coli cells through transformation. From a successful transformation, we expected the bacterial cells to translate the inserted EGFP sequence into its protein form. The bacteria cultures were plated on petri dishes containing growth supplement, Luria Broth (LB), an antibiotic: Kanamycin, and IPTG which induced the fluorescence property within successfully transformed bacterial colonies. Different variants of the petri dishes were also included as control and unknown.
Miller, Kenneth R. and Joseph S. Levine. “Chapter 12: DNA and RNA.” Biology. Upper Saddle River: Pearson Education, Inc., 2002. Print.
There are three main divisions of living organisms: Prokaryotes, eukaryotes and archaea. This essay will outline the division between the prokaryotic and eukaryotic organisms and explore the reasoning behind such differences with regard to general structure, storage of deoxyribonucleic acid and its replication, metabolic processes, protein synthesis and ribonucleic acid processing.
... the codon for the amino acid methionine is added the head of each chain.
... This observation gives evidence to the idea that polymerization of LC domains should precede their binding to CTD of RNA polymerase II.
(Kesssel,A. and Ben-Tal N. (2011) Introduction to Proteins: Structure, Function and Motion, London: CRC Press)
“The effect of protein synthesis inhibition on the entry of messenger RNA into the cytoplasm of sea urchin embryos”, Hogan and Gross. J. Cell Biol. 49(3):692-701.
"The Species of the Secondary Protein Structure. Virtual Chembook - Elmhurst College. Retrieved July 25, 2008, from http://www.cd http://www.elmhurst.edu/chm/vchembook/566secprotein.html Silk Road Foundation. n.d. - n.d. - n.d.
It breaks the hydrogen bonds formed between opposing strands of DNA with energy formed through the hydrolysis of ATP to ADP and inorganic phosphate (Hartsuiker, 2013). The separation of strands is necessary as newly formed strands need to be transcribed using the nucleotide sequence of an open DNA strand. The protein is built around 6 sub-units which form an hexameric ring with assymetic symmetry.
...cture. Regions 3 and 4 are also complementary and can form this same structure. Which of the two structures form is dependent on the level of trp in the environment. If trp is abundant, then as the ribosome translates over region 1, charged tRNA-trp will arrive at the codon site allowing for fast translation and quick arrival and partial overlap of region 2 making it unavailable to associate with region 3. Region 3 then associates with region 4 signaling for termination and for RNA polymerase to disassociate from the DNA before it transcribes the structural genes. When the environment is starved of tryptophan, as the ribosome translates over region 1, the ribosome stalls as it waits for charged tRNA-trp. This delay allows for the association of region 2 with region 3 preventing the pairing of regions 3 and 4 and permitting the transcription of the structural genes.
end of the tRNA and the tRNA binds to the mRNA. Cells posses over 20
A polypeptide chain is a series of amino acids that are joined by the peptide bonds. Each amino acid in a polypeptide chain is called a residue. It also has polarity because its ends are different. The backbone or main chain is the part of the polypeptide chain that is made up of a regularly repeating part and is rich with the potential for hydrogen-bonding. There is also a variable part, which comprises the distinct side chain. Each residue of the chain has a carbonyl group, which is good hydrogen-bond acceptor, and an NH group, which is a good hydrogen-bond donor. The groups interact with the functional groups of the side chains and each other to stabilize structures. Proteins are polypeptide chains that have 500 to 2,000 amino acid residues. Oligopeptides, or peptides, are made up of small numbers of amino acids. Each protein has a precisely defined, unique amino acid sequence, referred to as its primary structure. The amino acid sequences of proteins are determined by the nucleotide sequences of genes because nucleotides in DNA specify a complimentary sequence in RNA, which specifies the amino acid sequence. Amino acid sequences determine the 3D structures of proteins. An alteration in the amino acid sequence can produce disease and abnormal function. All of the different ways
Ribozymes are catalytic molecules that cleave the ribonucleic acid (RNA) at specific sequences (Gesteland et al. 2006). RNA is the nucleic acid that is made in the process of transcription; when the deoxyribonucleic acid (DNA) anneals, it transcribes itself into a linear stranded molecule called RNA. In order for RNA to synthesise proteins, it requires catalytic enzymes to perform certain chemical reactions. In the past, it was thought that all chemical reactions are catalysed by protein enzymes; however, in the eighties this hypothesis was disproved as Thomas Cech and Sydney Altman discovered that RNA is able to carry out self-catalysing activities which were named as ribozymes because they perform similar functions as the protein enzymes (Jaeger, 1997). Even though, RNA ribozymes lack the functional groups diversity found in protein enzymes, they are able to carry out their own catalytic reactions due to their tendency to fold into a 3D structure and form helices by Watson-Crick base pairing role (Kiehntopf et al. 1995). Ribozymes are now play critical role in the understanding of biochemistry, as they have the ability to catalyse some of the most important chemical reactions such as RNA splicing as well as the synthesis of peptides, for instance ribozymes can speed up the phosphoryl transfer chemical reactions by 1011 folds. This review will describe the structure, sources and applications of ribozymes.
The first stage of the process is the unwinding of old strands of the parent DNA molecule. The two strands of the double helix are first separated by enzymes. Then, each strand acts as a template for t...
The information form DNA is used as a template and rewritten onto RNA resulting in the molecule messenger RNA (mRNA) which carries a genetic message from DNA to the protein synthesizing part of the cell. Translation is the synthesis of a polypeptide using information provided by mRNA. In the ribosomes, the cell translates the nucleotide sequence of mRNA molecule into the amino acid sequence of a polypeptide. Transcription and translation occur in both prokaryotes and eukaryotes. In eukaryotes, the nuclear membrane separates transcription and translation, while in prokaryotes, there is no membrane so mRNA may begin transcription before translation is complete. Eukaryotic RNA transcripts are modified through RNA processing to yield finished