# Total number of proteins per cell

Range ~5e+7 Molecules/cell Budding yeast Saccharomyces cerevisiae Futcher B, Latter GI, Monardo P, McLaughlin CS, Garrels JI. A sampling of the yeast proteome. Mol Cell Biol. 1999 Nov19(11):7357-68. p.7358 left column 4th paragraphPubMed ID10523624 A haploid yeast cell contains about 4×10^-12g of protein (refs 1, 15). Assuming a mean protein mass of 50kDa, there are about 50×10^6 molecules of protein per cell. 6×10^23[proteins/mole]×4×10^ -12[gram]/50000[gram/mole]=~50×10^6proteins P.7358 left column 4th paragraph: "A haploid yeast cell contains about 4×10^-12g of protein (refs 1, 15). Assuming a mean protein mass of 50 kDa, there are about 50×10^6 molecules of protein per cell. There are about 1.8 methionines per 10kDa of protein mass, which implies 4.5×10^8 molecules of methionine per cell (neglecting the small pool of free Met). [Researchers] measured (i) the counts per minute in each spot on the 2D gels, (ii) the total number of counts on each gel (by integrating counts over the entire gel), and (iii) the total number of counts loaded on the gel (by scintillation counting of the original sample). Thus, [they] know what fraction of the total incorporated radioactivity is present in each spot. After correcting for the methionine (and cysteine [see below]) content of each protein, [they] calculated an absolute number of protein molecules based on the fraction of radioactivity in each spot and on 50×10^6 total molecules per cell." See BNID 104313 Uri M 106198