TABLE 2.
Identification of ssrA(His6) peptide tagging sites
FLAG-TrxA-ArfA fusion proteins were overproduced in E. coli rnc+ ssrA(his6) cells, and ssrA(His6)-tagged proteins purified for identification by electrospray ionization-mass spectrometry.
| Fusion construct | ssrA(His6)-tagged ArfA residuea | Observed mass | Predicted mass |
|---|---|---|---|
| Da | |||
| flag-trxA-arfA′(Eco) | Ala53 | 15,234 | 15,235.11 |
| Ser54 | 15,321 | 15,322.19 | |
| Gly55 | 15,378 | 15,379.24 | |
| flag-trxA-arfA′(Vfi) | Pro60 | 15,031 | 15,031.96 |
| Tyr61 | 15,194 | 15,195.13 | |
| Ala64 | 15,480 | 15,481.46 | |
| Thr65 | 15,582 | 15,582.57 | |
| flag-trxA-arfA′(Pmu) | Pro63 | 15,031 | 15,031.96 |
| Asp64 | 15,147 | 15,147.05 | |
| Tyr65 | 15,308 | 15,310.22 | |
| flag-trxA-arfA(Hin) | Glu62 | 21,754 | 21,755.86 |
| Lys63 | 21,882 | 21,884.04 | |
| Pro64 | 21,979 | 21,981.15 | |
| Asp65 | 22,094 | 22,096.24 | |
| flag-trxA-arfA(Pmi) | Ala54 | 20,808 | 20,809.62 |
| Ser55 | 20,895 | 20,896.69 | |
| flag-trxA-arfA(Eco)b | Ala53 | 20,737 | 20,737.43 |
| Ser54 | 20,823 | 20,824.5 | |
| flag-trxA-arfA(Ngo)b | Gly51 | 20,416 | 20,419.17 |
| Phe52 | 20,563 | 20,566.35 | |
| Asp53 | 20,679 | 20,681.43 | |
| Val55 | 20,881 | 20,881.67 | |
| Pro56 | 20,978 | 20,978.79 | |
a Residue numbers correspond to their positions in the native ArfA proteins and residues in bold represent the major species detected by mass spectrometry.
b These constructs were transcribed by E. coli RNA polymerase from the Ptrc promoter.