PROTEIN SYNTHESIS PART 1 What are the common structures and features of the vast
ID: 34299 • Letter: P
Question
PROTEIN SYNTHESIS PART 1
What are the common structures and features of the vast majority mRNAs? mRNA translation and decay rates vary widely among different mRNAs, yet all mRNAs share the same regulatory structures. How is this possible? What does nuclear import of proteins and nuclear export of proteins/RNAs have in common? What is different about mRNA export from most other classes of cellular RNA? How do cells ensure that each tRNA is coupled to the correct amino acid? What would happen if amino acylation paired tRNAs to multiple amino acids? How does a ribosome select the right reading frame for translating an mRNA? How does translation initiation occur in eukaryotic cytoplasm? What are some of the possible consequences of starting in the wrong reading frame? How does GTP hydrolysis by elongation factor eEF1A contribute to the fidelity of protein synthesis? Why do Eukaryote nuclear genomes still have bacteria-like EF-Tu and EF-G in addition to their cytoplasmic eEF1 and eEF2 proteins? Compare the mitochondrial and chloroplast ribosomes to the cytoplasmic ribosomes? Where do each of these three originate during evolution?Explanation / Answer
1)
An mRNA contains a 5’ CAP, which is made up of 5-methyl Guanosine and a 3’ poly adenosine tail (poly “A” tail). The internal sequences contain two types of typical sequences called exons and introns. The coding sequences are called exons and non-coding sequences are called introns.
2)
The degradation rate of an mRNA depends on several factors, which include length of entire sequence and length of poly-A tail. If an mRNA does not contain 5’ CAP and poly-A tail, they will degrade very easily by the exonucleases.
The 5’ CAP cannot be degraded by any exonuclease, because exonucleases do not have specificity toward 5-methyl Guanosine, but the poly-A tail can degrade by these enzymes. Hence, every mRNA has long poly-A tails (A20-250), but the variance in this length may have an effect on mRNA degradation.
3)
Nuclear import and export or proteins and RNAs is based on their NSL (nuclear localization signal) and Cap binding protein.
4)
Cells ensure that each tRNA is coupled to the correct amino acid by codon and anticodon interaction. If they both are interacted, then the amino acid delivered and forms peptide bond with growing peptide chain amino acid.
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