TABLE 3.
Masses of subunits of Nostoc cyt b6f complex measured by electrospray-ionization MS
| Subunit | Measured massa | Calculated massb | Modificationsc |
|---|---|---|---|
| Cytochrome f | 31,769 | 31,768 | + heme |
| Cytochrome b6 | 24,757 | 24,758 | - Met-1, + heme |
| Rieske ISP | 19,107 | 19,106 | - Met-1, +/- Ac |
| 19,064 | 19,064 | + Disulfided | |
| SuIV | 17,404 | 17,405 | - Met-1 |
| petG | 4,023 | 4,023 | N-Formyl |
| petM | 3,574 | 3,574 | N-Formyl |
| petN | 3,262 | 3,262 | N-Formyl |
| petL | 3,253 | 3,253 | N-Formyl |
a
Average mass, mean of two measurements.
b
Calculated average mass based upon natural isotopic abundances and available sequence modification data.
c
Modifications include removal of initiating methionine, N-formylation of N terminus (retention of initiating formylmethionine), acetylation (Ac), presence of heme, and disulfide bonds.
d
Calculated 19,066.43 - 2(1.0078) = 19064.41, and for the acetylated form: 19106.42.