Table I. Analysis of PSBR phosphorylation revealed three distinct phosphorylation sites.
To investigate PSBR phosphorylation in C. reinhardtii, we performed mass spectrometric analyses of thylakoid membranes using SIMAC for phosphopeptide enrichment (Thingholm et al., 2008). Subscript numbers indicate positions of phosphorylation sites within the unprocessed polypeptide. Phosphorylation site validation was done with phosphoRS (Taus et al., 2011).
| Peptide | No. of Phosphorylations | Observed Mass | Charge | Theoretical Mass | Posterior Error Probability | phosphoRS |
||
|---|---|---|---|---|---|---|---|---|
| Sequence Probability | Peptide Score | Site Probabilities | ||||||
| m | m | |||||||
| TDITKVGLNs40IEDPVVK | 1 | 1,906.969 | 2 | 1,906.965 | 3.99E-05 | 1 | 183.87 | T(1), 0.0; T(4), 0.0; S(10), 100.0 |
| t31DITKVGLNSIEDPVVK | 1 | 1,906.973 | 2 | 1,906.965 | 1.18E-09 | 0.95 | 192.88 | T(1), 94.5; T(4), 5.5; S(10), 0.0 |
| t31DITKVGLNs40IEDPVVK | 2 | 1,986.935 | 2 | 1,986.931 | 5.42E-06 | 0.94 | 181.60 | T(1), 93.9; T(4), 6.1; S(10), 100.0 |
| TDIt34KVGLNSIEDPVVK | 1 | 1,906.965 | 2 | 1,906.965 | 8.62E-16 | 1 | 202.86 | T(1), 0.4; T(4), 99.6; S(10), 0.0 |
| TDIt34KVGLNs40IEDPVVK | 2 | 1,986.932 | 2 | 1,986.931 | 8.62E-16 | 1 | 136.01 | T(1), 0; T(4), 100.0; S(10), 100.0 |
| VGLNs40IEDPVVK | 1 | 1,348.665 | 2 | 1,348.663 | 8.84E-16 | 1 | 149.95 | S(5), 100.0 |