14
votes
Why do 60S & 40S ribosomal subunits make an 80S ribosome (not 100S)?
When a complex mixture of particles undergoes ultracentrifugation, they separate based on their shape and mass due to the force applied by the centrifuge and the counteracting frictional force of the ...
12
votes
Why do 60S & 40S ribosomal subunits make an 80S ribosome (not 100S)?
The other two answers give nice detail, so I want to give a bit more mathematical answer here.
First, the S you are talking about is Svedberg units (of sedimentation coefficient, named after Swedish ...
11
votes
Can I use multiple bicistronic RBS sequences in a synthetic biological circuit?
That’s a great question and has lot of opportunities to explore. I am not sure anyone has followed up on this original BCD work systematically. We did try cloning these elements on a medium copy ...
10
votes
Accepted
Peptides neither produced by the ribosome or the non-ribosomal peptide synthase complexes
One peptide that comes to mind is the metabolically important reducing tripeptide glutathione — γ-L-Glutamyl-L-cysteinylglycine:
This is synthesized from cysteine, glutamate and glycine by reactions ...
8
votes
Accepted
Can ribosomes read ssDNA?
Summary
Messenger RNAs that are recruited to the ribosome for protein synthesis in vivo, need to satisfy particular structural requirements and must interact with the protein initiation factors that ...
8
votes
Accepted
How can good Shine–Dalgarno or Kozak sequences enhance translation?
I would strongly recommend looking in more detail into available resources for SD and Kozak sequences, wikipedia basically answers these questions and has plenty of further reading if you desire to ...
7
votes
Accepted
Structure of mitochondrial ribosomes
The wording of the question suggests that it may be useful to clarify the meaning of the numbers in the designations 70S, 50S, 30S etc. These are sedimentation coefficients in Svedberg units as ...
6
votes
Accepted
When does protein folding begin?
When does protein folding begin?
With reference to time you have asked, it can be after the translation has occurred (called Translational protein folding) or while translation is still occuring (...
6
votes
Accepted
Does the ribosome have protein kinase activity?
No — there is no ribosomal protein with protein kinase activity.
It is difficult to provide conclusive evidence for a negative statement, but the two objective points I can make in support of my view ...
5
votes
Accepted
Ribosomes producing proteins, but need proteins to be produced?
Ribosomes are the only means we know by which cells produce proteins. Consequently, all proteins are made by a ribosome, including the proteins that then become part of a new ribosome. It's never a ...
4
votes
What is the Shine–Dalgarno sequence?
According to this Wikipedia article:
"The Shine-Dalgarno (SD) sequence is a ribosomal binding site in
bacterial and archaeal messenger RNA, generally located around 8 bases
upstream of the ...
4
votes
Translation of Poly-U in the Nirenberg and Matthaei experiment
This is an intelligent question that highlights the ‘sleight of hand’ simplifications employed in many text books to make experimental science appear cleaner and more logical than is in fact the case. ...
4
votes
Accepted
Why does azithromycin not affect human mitochondria?
There are two general points that should be appreciated in relation to this question:
Your statement that mitochondria “have prokaryotic ribosomes” is a misleading simplification. Although ...
4
votes
Accepted
Why do ribosomes associate with rough endoplasmic reticulum but not other membranes?
Peptides that are destined to be either secreted or included in the cell membrane have a signal sequence that binds a protein called Signal Recognition Particle (SRP). The SRP will in turn bind to ...
3
votes
How is Open Reading Frame (ORF) chosen?
Tl Dr: In the rosalind example they are showing the 3 reading frames that stem from the definition of a reading frame(non-overlapping triplets), not an example of open reading frames. Open reading ...
3
votes
Accepted
Is there an Exit site (E-site) on the eukaryotic ribosome?
Prelude: Thinking about protein synthesis
I remember the time when there were only two sites on the ribosome, and when it became clear there were more, I resented the need to make my lecture notes ...
3
votes
Can ribosomes read ssDNA?
My question is whether translation can be done, either naturally or artificially, through a ribosome reading (single-stranded) DNA directly.
Ribosomes participate into the translation of mRNA into ...
3
votes
Accepted
The genetic code and the effect of point mutations on proteins
Nonambiguity refers to the fact that codon X will always code for the same amino acid.
Degeneracy refers to the fact that an amino acid can be coded for by many codons.
I rephrase the question to ...
3
votes
Accepted
How many proteins do all human ribosomes together produce per hour?
Regarding protein synthesis rate, here's an attempt at an estimate from bioenergetics:
ATP turnover in the human body is consider to be about 100 mol / day.
Protein synthesis is estimated to require ...
3
votes
Accepted
How the size of ribosomes are calculated?
Because Svedberg is not a measure of weight, but it is a measure of a relative sedimentation after centrifugation.
"It is defined as the ratio of a particle's sedimentation velocity to the ...
3
votes
Accepted
Does my reasoning about the first emergence of proteins make any sense?
As their name suggests, the majority of a ribosome's structure and function come from ribonucleic acid (RNA), not protein. While ribosomes are about 35%-40% protein on average, a majority of ribosomal ...
3
votes
Can I use multiple bicistronic RBS sequences in a synthetic biological circuit?
In the documentation for this recent cloning method from Richard Murray's group at Caltech (,https://doi.org/10.1021/acssynbio.8b00060) they include a parts library with various BCDs. I haven't ...
2
votes
Why does azithromycin not affect human mitochondria?
The endosymbiotic theory states that eukaryotic mitochondria were once freely-living bacteria that somehow migrated into the cell and began a symbiotic relationship.
However, just because the ...
2
votes
Accepted
Identification of proteins in this animation of a ribosome translating mRNA
The protein involved in "pushing" the tRNA and mRNA is the elongation factor EF-G. The protein involved in "transporting" the tRNA is the elongation factor EF-Tu.
Quoted from the Wikipedia articles:
...
2
votes
Accepted
Sequence of ribosomal RNA
Unequivocally, YES.
Before DNA sequencing was used to deduce the sequence of cloned or reverse-transcribed RNA molecules, slower and more cumbersome direct sequencing of RNA was performed using the ...
2
votes
Accepted
Why is translation so much faster in prokaryotes than eukaryotes?
Unless the poster can cite more recent papers to support the assertion regarding a difference in rates of prokaryotic and eukaryotic protein synthesis, I would say that this is incorrect.
Lacroute ...
2
votes
How does a ribosome gather tRNAs at a fast enough rate for Translation?
The answer is simply due to the random walk of the amino acids. Over small volumes, this process is incredibly quick and is also responsible for nucleotide delivery to polymerases as well proteins ...
2
votes
Do ribosomes read mRNA?
The first two sentences of the Wikipedia Ribosome article say:
The ribosome... serves as the site of biological protein synthesis (translation). Ribosomes link amino acids together in the order ...
2
votes
What prevents non-aminoacylated tRNA from binding to mRNA on the ribosome and disrupting protein synthesis?
Short answer
The codon-directed non-enzymic binding of tRNA (aminoacylated or not) to the A-site of the ribosome is much weaker than the (normal) binding of aminoacyl-tRNA complexed to EF-Tu/EF-1, the ...
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