Insights & Perspectives
What is the total number of protein molecules per cell volume? A call to rethink some published values
Article first published online: 20 SEP 2013
© 2013 The Author. Bioessays published by WILEY Periodicals, Inc.
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Volume 35, Issue 12, pages 1050–1055, December 2013
How to Cite
Milo, R. (2013), What is the total number of protein molecules per cell volume? A call to rethink some published values. Bioessays, 35: 1050–1055. doi: 10.1002/bies.201300066
- Issue published online: 18 NOV 2013
- Article first published online: 20 SEP 2013
- European Research Council (Project SYMPAC – 260392)
- Israel Science Foundation. Grant Number: 750/09
- Helmsley Charitable Foundation
- cell biology by the numbers;
- mass spectrometry;
- protein abundance;
- proteomic calibration;
- protein copy numbers;
- proteins per cell;
- quantitative proteomics
Novel methods such as mass-spectrometry enable a view of the proteomes of cells in unprecedented detail. Recently, these efforts have culminated in quantitative measurements of the number of copies per cell for most expressed proteins in organisms ranging from bacteria to mammalian cells. Here, we estimate the expected total number of proteins per unit of cell volume using known parameters related to the composition of cells such as the fraction of cell mass that is protein, and the average protein length. Using simple arguments, we estimate a range of 2–4 million proteins per cubic micron (i.e. 1 fL) in bacteria, yeast, and mammalian cells. Interestingly, we find that measured values that are reported for fission yeast and mammalian cells are often about 3–10 times lower. We discuss this apparent discrepancy and how to use the estimate as benchmark to recalibrate proteome-wide quantitative censuses or to revisit assumptions about cell composition.