Table 1.
Summary of results obtained by assessing the role of the covarying residues Gln49 and Arg104 in CcmC and CcmE, respectively (42), by mutagenesis on the entire E. coli System I operon and subsequent quantification of the relative amounts of holo-CcmE and exogenously expressed cytochrome c550 produced in vivo
For several variants, levels of holo-c550 were assessed first. WT amounts of c550 indicate that the mutation has no effect on the maturation process; in these cases, quantification of holo-CcmE was omitted (entries marked with — in the “Holo-CcmE level” column).
| Variant | Holo-c550 level | Holo-CcmE level |
|---|---|---|
| Q49A-CcmC | WT level | Small increase |
| R104A-CcmE | WT level | WT level |
| Q49A-CcmC/R104A-CcmE | No holo-c550 | Holo-CcmE accumulation |
| Q49R-CcmC/R104Q-CcmE | WT level | — |
| Q49E-CcmC | WT level | — |
| Q49I-CcmC/R104I-CcmE | WT level | — |
| Q49S-CcmC | WT level | — |
| R104S-CcmE | WT level | — |
| Q49S-CcmC/R104S-CcmE | WT level | — |
| Q49C-CcmC | WT level | — |
| R104C-CcmE | WT level | — |
| Q49C-CcmC/R104C-CcmE | WT level | — |
| Q49A-CcmC/R104V-CcmE | No holo-c550 | Holo-CcmE accumulation |
| Q49V-CcmC/R104A-CcmE | No holo-c550 | Holo-CcmE accumulation |
| Q49V-CcmC/R104V-CcmE | No holo-c550 | Holo-CcmE accumulation |
| Q49K-CcmC/R104A-CcmE | WT level | — |