Subsystem: Programmed frameshift
This subsystem's description is:
Peptide chain release factor 2 --
Peptide chain release factor 2 is resposible for terminating translation at UGA codons. When a UGA is encountered, the ribosome stalls, because there is no appropriate tRNA. Release factor 2 can mimic the tRNA, leading to the release of the peptide from the tRNA.
Peptide chain release factor 2 unshifted fragment --
In most organisms, the release factor 2 gene has in inframe UGA stop codon about 25 codons from the start of translation. If there is sufficent release factor 2, translation stops at this point, releasing a short peptide: "Peptide chain release factor 2 unshifted fragment". Not all of these are currently annotated.
If there is not sufficient release factor 2, the ribosome can slip forward one nucleotide, sliding from the UGA to a GAN (usually GAC, encoding Asp) codon and then continuing to produce the full protein. The amino acid before the stop is most often a CUU Leu codon. One other common (but not universal) feature of the frame shifting site is a strong ribosome binding site (but no corresponding start codon).
programmed frameshift-containing --
The release factor 2 genes that include an inframe stop codon are indicated by the additional role "programmed frameshift-containing". This annotation is very nearly comprehensive.
Mycoplasmas use UGA as a second codon for tryptophan. Almost as if planned, they do not have release factor 2.
For more information, please check out the description and the additional notes tabs, below
| Diagram | Functional Roles | Subsystem Spreadsheet | Description | Additional Notes | |||||||||
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