Estimated rate of peptide chain degradation by proteasome in Hela cell extract

Range ~0.2 peptide chains/min
Organism Eukaryotes
Reference Hendil KB, Hartmann-Petersen R, Tanaka K. 26 S proteasomes function as stable entities. J Mol Biol. 2002 Jan 25 315(4):627-36. p.631 right column 3rd paragraphPubMed ID11812135
Method "These proteasomes degraded about 0.4-0.5% of the bulk protein per hour, or around 4.5 mg per gram of protein. SDS-PAGE shows that the average molecular mass of cell proteins is about 50 kDa (not shown), so this corresponds to about 9×10^8 moles of peptide chain. In other words, each proteasome degraded 9?10^-8/ 8?10^-9 or approximately 11 peptide chains per hour or 0.2 chain per minute."
Comments Rate is equivalent to about 1 aa/s. From some back of the envelope calculation it seems this at least an order of magnitude too slow to explain protein turnover in cell lines. Probably the cell extract rate is lower than the actual in vivo rate.
Entered by Uri M
ID 108032