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Updated: Aug 2, 2026
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A Convenient and General Expression Platform for the Production of Secreted Proteins from Human Cells
Published on: July 31, 2012
How many proteins are there in a typical mammalian cell?
Clinical Chemistry
|April 1, 1982
Summary
Mammalian cells have fewer detected proteins than expected based on mRNA. This study reveals rare messenger RNAs (mRNAs) are translated at very low rates, limiting protein diversity.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- A significant discrepancy exists between the number of polysomal messenger RNA (mRNA) species and detected polypeptides in mammalian cells.
- Previous research has not fully explained this disparity, leaving the regulation of protein synthesis unclear.
Purpose of the Study:
- To investigate the reasons behind the lower-than-expected number of detected polypeptides compared to mRNA species in mammalian cells.
- To determine if technical limitations or translational regulation account for the observed protein paucity.
Main Methods:
- Analysis of polysomal mRNA and protein expression using high-resolution two-dimensional polyacrylamide gel electrophoresis.
- Comparative assessment of mRNA abundance and corresponding polypeptide detectability.
Main Results:
- Technical factors do not explain the limited number of detected polypeptides.
- The translation products of rare mRNAs would be detectable if translated proportionally to their abundance.
- A large majority of rare mRNAs are translated at significantly lower rates than average, or not at all.
Conclusions:
- The limited number of detected polypeptides is primarily due to translational regulation, not technical limitations.
- Mammalian cells may possess a restricted set of approximately 2000 physiologically significant primary gene products (polypeptides).
- This suggests a regulatory mechanism controlling protein output from the transcriptome.
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