A Cell Can Hold How Many Protein Molecules, Exactly?
It sounds like the opening to a really cheesy science joke
How many protein molecules are there in a cell?
But the answer isnt a punch line, its 42 million.
As ScienceDaily reports, scientists have finally put a number to this age-old question, concluding years of speculation and paving the way for further research into the effect protein levels could have on an organisms health.
Proteins do much of the heavy-lifting when it comes to the actual work that cells perform.
Not only that, but many diseases can be traced back to having too much or too little of a given protein. The more that researchers are able to find out about what proteins cells actually contain (and how many!), the more they will be able to learn about how protein abundance is controlled and potentially be able to fix things when protein levels go awry.
Up to this point, protein abundance has been studied in a variety of different ways, which makes it hard to compare data between different labs and studies.
For example, some researchers have estimated protein levels by using fluorescent tags on protein molecules and extrapolating abundance by how much the cells glow. But with variance in instrumentation, different labs would record different levels of emitted light. Other researchers and labs would use entirely different approaches. Because of this, it was difficult to conceptualize how many proteins there are in a cell, since the data was consistently reported so differently.
To begin quantifying the number of protein molecules per cell, researchers looked to bakers yeast a single-cell microbe that is easy to study and offers a look at the makeup and function of a basic cell. Also helpful is the fact that numerous studies exist that measured the abundance of all yeast proteins, offering a comprehensive data set for benchmarking and analysis.
For the first time, it was possible to calculate how many molecules of each protein existed in a cell, with the total number of molecules estimated at around 42 million.
Not only that, but researchers were able to discern mechanisms by which cells were able to control the levels of different proteins, which could eventually help researchers study similar things in human cells and find potential molecular roots of disease. They were also able to demonstrate a correlation between protein supply and role in the cell, which allows for potential future research into using abundance data to predict protein functions.
Interested in learning more?
University of Toronto. "A cell holds 42 million protein molecules, scientists reveal." ScienceDaily. ScienceDaily, 17 January 2018. www.sciencedaily.com/releases/2018/01/180117131202.htm.
Brandon Ho, Anastasia Baryshnikova, Grant W. Brown. Unification of Protein Abundance Datasets Yields a Quantitative Saccharomyces cerevisiae Proteome. Cell Systems, 2018; DOI: 10.1016/j.cels.2017.12.004
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