Kozak consensus sequence

The sequences flanking the initiator AUG in the SFV 26 S RNA are accommodated within the structure CAXXAUGa that has been considered a possible consensus sequence for a eukaryotic initiation site for translation (Kozak, 1981). Downstream from the initiation codon by 7 bases is a sequence of 11 nucleotides (AUCCCUACGCA), 9 of which (those underlined) are complementary to the purine-rich tract close to... 

The binding of the 43S complex to the capped 5 -end of the mRNA is followed by its migration and scanning until the first AUG codon is encountered (Kozak, 1989). Although there are some exceptions, more than 90% of cellular mRNAs appear to have GCC GCC A/GCC AUG GG as the consensus sequence for the... 

Once associated with mRNA, the pre-initiation complex scans downstream to locate a start codon (AUG). This process is driven by ATP, and requires the helicase activity of an elF. The start codon is recognised by base paring between the anti-codon on tRNA and the AUG on the mRNA. Codon-anticodon interaction is facilitated by yet more elFs. Usually, the first AUG codon that is encountered is used, especially if it is surrounded by the so called Kozak consensus sequence (named after its discoverer Marilyn Kozak). Occasionally a later AUG is used if the first AUG not in the context of a consensus Kozak sequence, or is very close to the 5 cap. This is in contrast to prokaryotes, where the AUG that will act as a start codon is located at the future P site by the position of the ribosome after base-pairing between the 16S rRNA of the ribosome and the Shine Dalgamo sequence. 

Initiation enhancing Kozak consensus sequence Shine-Dalgamo consensus sequence... 

Fig. 4. Nucleotide and deduced amino acid sequence of a cDNA clone encoding human precystatin C. Numbering of the nucleotide sequence starts at the first nucleotide and proceeds in the 5 to 3 direction. Amino acid numbering begins with residue 1 of the mature protein (Gil) and the putative hydrophobic signal sequence thus comprises residues —26 to — 1. The Kozak initiation consensus and the polyadenylation signal are underlined.

Based on the analysis of 5 noncoding (5 NC) sequences from 699 vertebrate mRNAs, a consensus initiation sequence (also called Kozak sequence) has been identified as 5 -CC(A/G)CCAUGG—3, in which the nucleotides at —3 (Pu) and -1-4 seem to be particularly important (5). Database analysis of approximately 2600 vertebrate mRNAs provided further evidence for strong but not exactly identical trinucleotide biases at the —3, —2, and —1 positions as (A/G)NCAUG... 

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