Table 2.
Calculated properties of amino acids and peptides.
| derived property and source | value |
|---|---|
| mean MW of 20 common AAs | 136.90 g mol−1 |
| mean MW of the AAs found in E. coli: (% abundance) × (MW), where % abundance is from (mol AA/dry g) × (MW) × (100/total g AA per dry gram E. coli) | 133.37 g mol−1 |
| MW of average AA in a peptide: (mean AA MW) – (MW H2O) | 118.89 g mol−1 |
| MW of average AA in E. coli peptide: (weighted mean AA MW) – (MW H2O) | 115.35 g mol−1 |
| mass of protein in E. coli: (E. coli dry mass) × (% mass protein), where 55% is proteina | 1.5 × 10–13 g |
| mass of mean protein in E. coli: (avg. MW residue) × (mean E. coli polypep. length) | 32067 g mol−1 |
| mean mass of an AA in a peptide in E. coli: (weighted mean AA MW)/(NA) | 1.92 × 10–22 g |
| number of dry E. coli in a gram: 1/(dry mass of E. coli cell) | 3.6 × 1012 |
| mass of average weighted AA residue in E. coli: (MW mean weighted AA residue)/(NA) | 1.915 × 10–22 g |
| number of AAs in proteins in E. coli: (dry mass E. coli protein)/(mass of average AA residue in E. coli in a protein) | 7.83 × 108 |
| number of proteins in E. coli: (number of AAs in proteins in E. coli)/(mean number AA per protein in E. coli) | 2.82 × 106 |
| concentration of average protein inside an E. coli: ((mean number of protein copies in E. coli cytoplasm)/(NA)) × (volume of aqueous portion of E. coli) | 8.7 × 10–6 M |
| average concentration of 17 free AA in E. coli cytosolb | 6.5 mM |
| number of polymerizations required to make all the protein in E. coli: (number of AA in proteins) – (number of proteins) | 7.80 × 108 |
| number of polymerizations required to make all the peptide bonds in a dry gram of E. coli: (AA in E. coli peptides per cell) × (number dry E. coli in a gram) | 2.82 × 1021 |
| Gibbs energy per peptide bond formed at 25°C and 1 bar for [AA] = 6.5 mM and [P278] = 8.7 µM (see text) | 6.76 × 10–20 J |
| Gibbs energy at 25°C and 1 bar required to make all the peptide bonds in a dry gram of E. coli for [AA] = 6.5 mM and [P278] = 8.7 µM: (ΔGr° per bond) × (number of peptide bonds per dry gram) | 0.191 kJ (g cell)−1 |
AA, amino acid; MW, molecular weight; NA, Avogadro's number.
aThe amino acid mass in a dry gram of E. coli is 641.8 mg (table 1). A dry gram contains 5081 µmol total AA [144] and 40.08 µmol of this is free, monomer AA [145]. Therefore, a dry gram of E. coli cells contains 5041 µmol of polymerized amino acids. The same number of moles of water converted into mass is 90.8 mg H2O. So, per dry gram, E. coli is 641.8 – 90.8 mg = 551 mg or 55% protein.
bConcentration data used to calculate average taken from [145].