Codon start

In addition to codons for ammo acids there are start and stop codons Protein biosynthesis begins at a start codon and ends at a stop codon of mRNA The start codon IS the nucleotide triplet AUG which is also the codon for methionine The stop codons are UAA UAG and UGA... 

Section 28 12 The start codon for protein biosynthesis is AUG which is the same as the codon for methionine Thus all proteins initially have methionine as their N terminal ammo acid but lose it subsequent to their formation The reaction responsible for extending the protein chain is nucleophilic acyl substitution... 

Lipoxygenase AVNTR polymorphism in 100 bp upstream from the ATG start codon is associated with transcription efficiency. Differences in response to 5-lipoxygenase inhibitors and leucotriene receptor antagonists. 

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... 

The mRNA is read continuously from a start codon (AUG) to a termination codon (UAA, UAG, UGA). 

Figure 4.2. Schematic illustration of directional cloning of PCR products. The sequence 5 CACC is required at the 5 end of the PCR product for directional topoisomerase-mediated cloning. In the example shown, the 5 -CACC sequence is appended immediately 5 of the ATG start codon of the gene to he inserted.

Lucotte G, Mercier G, Burckel A. The vitamin D receptor FokI start codon polymorphism and bone mineral density in osteoporotic postmenopausal French women. Clin Genet 1999 56[3] 221 224. 

Valasek, L., Nielsen, K. H., Zhang, F., Fekete, C. A., and Hinnebusch, A. G. (2004). Interactions of Eukaryotic Translation Initiation Factor 3 (eIF3) Subunit NIPl/c with elFl and eIF5 promote preinitiation complex assembly and regulate start codon selection. Mol. Cell. Biol. 24, 9437-9455. 

There is one start codon (initiation codon), AUG, coding for methionine. Protein synthesis begins with methionine (Met) in eukaryotes, and formylmethionine (finet) in prokaryotes. 

The charged initiator tRNA becomes bound to the AUG start codon on the messt e through base pairing with its anticodon. The initiator tRNA in prokaryotes carries fmet, whereas the initiator tRNA in eukaryotes carries Met. 

Figure 1.8 Translation of messenger RNA. The attachment of a ribosome to the mRNA involves protein initiation factors and the recognition of a particular base sequence, the start codon. A single mRNA can be simultaneously translated by more than one ribosome, forming a polyribosome. Synthesis occurs in the direction from the 5 end of messenger RNA to the 3 end. For further details of protein synthesis see Chapter 20.

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