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Ribosomes are essential for protein synthesis in all living organisms. Prokaryotic and eukaryotic ribosomes both contain a scaffold of ribosomal RNA (rRNA) on which are arrayed an extensive variety of ribosomal proteins (RP). [4] Ribosomopathies can arise from abnormalities of either rRNA or the various RPs. [citation needed]
Cell damage (also known as cell injury) is a variety of changes of stress that a cell suffers due to external as well as internal environmental changes. Amongst other causes, this can be due to physical, chemical, infectious, biological, nutritional or immunological factors. Cell damage can be reversible or irreversible.
The heat shock response (HSR) is a cell stress response that increases the number of molecular chaperones to combat the negative effects on proteins caused by stressors such as increased temperatures, oxidative stress, and heavy metals. [1]
The permissive temperature is the temperature at which a temperature-sensitive mutant gene product takes on a normal, functional phenotype. [2] When a temperature-sensitive mutant is grown in a permissive condition, the mutant gene product behaves normally (meaning that the phenotype is not observed), even if there is a mutant allele present.
A third protein, RaiA (ribosome-associated inhibitor A) is thought to both inactivate 70S ribosomes alone and stabilize them, preventing them from being converted into 100S ribosomes. [2] Most non-gammaproteobacteria, as well as some plant plastids, instead contain a HPF homologue that can form 100S ribosomes by itself.
[1] [2] Eukaryotic ribosomes are also known as 80S ribosomes, referring to their sedimentation coefficients in Svedberg units, because they sediment faster than the prokaryotic ribosomes. Eukaryotic ribosomes have two unequal subunits, designated small subunit (40S) and large subunit (60S) according to their sedimentation coefficients.
A new study explains how mitochondria act as “reservoirs” to store NAD for cells to use, which could help scientists come up with NAD-boosting therapies to combat aging and age-related diseases.
It is known that ribosomes pause at distinct sites, but the reasons for these pauses are mostly unknown. Also, the ribosome pauses if the pseudoknot is disrupted. 10% of the ribosome pauses at the pseudoknot and 4% of the ribosomes are terminated. Before the ribosome is obstructed it passes the pseudoknot. [17]