There is papers out there who have tested it, the correlation coefficient is between 0.4 and 0.7 in the range of the correlation of shoe size to yearly income....Also, taking the same protein in 20 different tissue or different proteins/genes in the same tissue, the difference between single data points can be 3 orders of magnitude, for example 1 000 RNA molecules per cell may result on 10 000 or 10 000 000 proteins per cell.

If you can't find the papers, I can send you the titles.

Hi Guruprasad

Theoretically amount of RNA should be protportional to the level of protein and in many cases it is also true...but it will be also dependent upon the half lives of the mRNA as well as that of protein...and also many other interactions that regulate protein synthesis...e.g. small RNAs regulate gene expression by several ways (other than degradation of the transcript) and one of the way is 'sequestring the transcript' or other non degradative control mechanims....in such cases the trasncript is abundant but is not available for translation...

You may find some more examples where the this relationship between mRNA levels and protein levels may not be exactly proportional

bye

I would say no. I am working on changes in protein abundance with age and am comparing my data with the published mRNA data on the same topic.I find that although mRNA might be differentially expressed, its corresponding protein does not and vice versa. However i have seen a few 9like 2 out 20) cases that are in agreement.

It does not have to be necessary the case taking into account microRNA-mediated silencing of mRNA, post-transcriptional modification of mRNA and post-translational modifications of protein which might lead to degradation/down- or upregulation of either one.

There is papers out there who have tested it, the correlation coefficient is between 0.4 and 0.7 in the range of the correlation of shoe size to yearly income....Also, taking the same protein in 20 different tissue or different proteins/genes in the same tissue, the difference between single data points can be 3 orders of magnitude, for example 1 000 RNA molecules per cell may result on 10 000 or 10 000 000 proteins per cell.

If you can't find the papers, I can send you the titles.

hi Guru,

i think the other two posts have already suggested this, but i will add to the discussion.

protein levels can be influenced by the regulation of gene(mRNA) transcription/translation as well as post-translational degradative pathways (e.g. ubiquitin-proteasome pathway). while gene levels can be regulated by the protein it encodes (positively or negatively), the relative amounts of the gene aren't necessarily relative to the levels of protein due to its independent methods of regulation.

with that said though, i think it's safe to say that the bottleneck in protein production is the amount of the encoding gene that's around in the cell. in other words, low levels of gene A = low levels of protein A (generally speaking). however, high levels of gene B don't always = high levels of protein B for the reasons i gave in the first paragraph along with what Maggy and Ajay stated in their posts.

this is not meant to be comprehensive, but i hope this is helpful.

thank you for all interesting and valuable suggestions. in these cases quantitative measurement of protein using RT PCR how far holds effective and accurate?

I think the best way to quantify your protein of interest is using monoclonal antibody. You can try ELISA (quantitative) or Westernblotting (semi-quantitative).

There is often no correlation between mRNA and protein levels. You are assuming that all mRNAs translate one single protein, and their synthesis and degradation rates are equal. Unfortunately, the proteome is exceedingly more complex than this. As well as other points mentioned above, mRNAs may be differentially spliced and there are a multitude of different post-translational modifications. With this in mind, applying RT PCR to infer a protein abundance level is crazy talk. If you have access to a decent antibody, perform a simple Western blot. Or consider more thorough proteomic approaches; array-, gel-or mass spectrometry-based depending on your starting material, protein yields and protein(s) of interest.

can you help me how can i isolate the protein from human blood ? any idea or protocal

There is data out there that shows that ~60% of the time, the amount of mRNA in a cell is directly proportional to the level of protein coded by that mRNA. So yes and No to your question. You have to imperically determine this correlation in your cells. The more important a protein is, the more its mRNA may be transcribed.

@ Alagamuthu - I think you may want to post your question in a separate thread so that more people may be able to see it.

To attempt an answer to your question, I first have to ask whether you want to look at extracellular proteins, proteins within peripheral blood mononuclear cells (PBMC), or red blood cells? You can separate all of these fractions by using Ficoll Paque solution (follow manufacturer protocol). Next, take whichever fraction you need and prepare samples for protein detection via western blot (assuming you know which protein you are looking for and have a good antibody against that protein).

Hi,

Detecting mRNA levels and their prospective proteins is important because there is a poor correlation between transcription and translation and that proteins are not proportional to the levels of corresponding mRNA. This is due to the many regulation  processes that separates transcription and translation and affect protein and mRNA.

There is a poor correlation between mRNA and its relevant protein level. It's better to check both levels. It's reasonable to see high protein level with high mRNA level but, the protein concentration is affected by many steps in transcription and translation as well as degradation.  On the other hand, you may have low mRNA expression and high levels of protein (if the protein is directly influences its expression, a negative feedback (downregulate mRNA expression).

mRNA quantity is not directly related to protein quantity. It depends on protein coding power which is a complex subject. However one factor that affects that is the existence of alternative starting codon in 5'UTR which inhibit the translation in normal conditions.

Take this article for example

http://www.sciencedirect.com/science/article/pii/S0378111916306989