Directed Protein Synthesis

H Translation is the process by which mRNA directs protein synthesis. Each mRNA is divided into codons, ribonucleotide triplets that are recognized by small amino acid-carrying molecules of transfer RNA (tRNA), which deliver the appropriate amino acids needed for protein synthesis. 

Translation (Section 28.5) The process by which the genetic information transcribed from DNA onto mRNA is read by tRNA and used to direct protein synthesis. 

The flow of biological genome knowledge is from DNA to RNA via transcription, and from RNA to direct protein synthesis via translation. 

Why is it essential to have trinucleotides rather than dinucleotides as codons for directing protein synthesis ... 

Removal of introns from hnRNA to leave only the exons or gene regions involved in directing protein synthesis in the finished mRNA is accomplished within the nucleus by processing on spliceosomes (Figure 11-4). 

DNA directing Protein Synthesis in a Cell The DNA directed protein synthesis occurs in two steps—... 

Translation The mRNA directs protein synthesis in the cytoplasm of the cell with the help of rRNA and tRNA. This process is called translation. The mRNA synthesized above gets attached to very small ribosome particles (60% rRNA and 40% protein). On the ribosome, mRNA serves as the template for protein synthesis. 

The absence of a nuclear membrane is a characteristic of bacteria that has a profound effect on transcription. Bacterial transcripts are processed rapidly, and their 5 ends often enter ribosomes and are directing protein synthesis, while the 3 ends of the genes are still being transcribed. In contrast, most eukaryotic RNA transcripts must be processed and transported out of the nucleus before they can function. As consequence, many aspects of the control of transcription differ between prokaryotes and eukaryotes. 

Three processes take place in the transfer of genetic information Replication is the process by which identical copies of DNA are made and genetic information is preserved. Transcription is the process by which messenger RNA is produced. Translation is the process by which mRNA directs protein synthesis. 

Expression. The production of a particular protein in a culture of bacterial cells. The production of such a protein is controlled by placing a gene encoding the protein of interest into a plasmid capable of directing protein synthesis. 

Plasmid cDNA-directed protein synthesis in a coupled eukaryotic in vitro transcription-translation system. Nucleic Acids Res. 20, 4987-4995. 

Biochemists refer to RNA synthesis as transcription. Transcription is the process of synthesizing ribonncleic acid (RNA). Synthesis takes place within the nnclens of eukaryotic cells or in the cytoplasm of prokaryotes and converts the genetic code from a gene in deoxyribonucleic acid (DNA) to a strand of RNA that then directs protein synthesis. 

Fig. 14.4. A schematic view of a eukaryotic gene, and steps required to produce a protein product. The gene consists of promoter and transcribed regions. The transcribed region contains introns, which do not contain coding sequence for proteins, and exons, which do carry the coding sequences for proteins. The first RNA form produced is heterogenous nuclear RNA (hn RNA), which contains both intronic and exonic sequences. The hnRNA is modified such that a cap is added at the 5 end (cap site), and a poly-A tail added to the 3 end. The introns are removed (a process called splicing) to produce the mature mRNA, which leaves the nucleus to direct protein synthesis in the cytoplasm. Py is pyrimidine (C or T).

Self-replicating RNA molecules, one of which can direct protein synthesis... 

How does messenger RNA direct protein synthesis The sequence of bases in a given mRNA determines the sequence of amino acids in a specified protein. The size of mRNA molecules varies with the size of the protein. 

Protein synthesis in prokaryotes takes place as a coupled process with simultaneous transcription of mRNA and translation of the message in protein synthesis. This is possible because of the lack of compartmentaliza-tion in prokaryotic cells. In eukaryotes, mRNA is transcribed and processed in the nucleus and only then exported to the cytoplasm to direct protein synthesis. 

In this paper, we have summarized our current understanding of the biochemical nature of the triazine binding site within the PS II complex. Studies using the proteolytic enzyme trypsin as a selective, surface-specific modifier of membrane polypeptides and the use of a photoaffinity triazine have been utilized separately to identify the triazine receptor protein as a 32-34 kilodalton (kDal) polypeptide of the PS II complex in peas (Pisum sativum L.). The nature of the covalent attachment of the photoaffinity probe has also enabled us to identify the triazine receptor protein as a product of chloroplast-directed protein synthesis this implies that the structural gene for the triazine receptor polypeptide is encoded on chloroplast DNA. 

The Triazine Receptor Protein is a Product of Chloroplast-Directed Protein Synthesis. Triazine resistance has been demonstrated from reciprocal crossing experiments to be inherited uniparentally through the female parent in campestris (16). 

Intracellular (cytoplasm and/or nucleus) Steroids and thyroid hormones Modification of RNA-directed protein synthesis and the transcriptional activity of responsive genes... 

Figure 6. Poly(U) directed protein synthesis with ribosomes from 6—10 and 23—24 month-old rat livers, as a function of concentration Phe, phenylalanine or correct" incorporation Leu, leucine or "incorrect incorporation Leu/Phe, incorrect / correct incorporation. Curves for young and old are virtually identical.

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