Quantification of Secretory Machinery in the Platelet
| Protein . | Calculated MW* (g/mol) . | ng/107 Cells . | Molecules/cell . | Concentration (μmol/L)† . |
|---|---|---|---|---|
| NSF | 247.9 × 103‡ | 7.0 ± 1.3 | 1,700 | 0.32 |
| (nρ = 11) | ||||
| α-SNAP | 33.2 × 103 | 3.1 ± 0.66 | 5,600 | 1.0 |
| (n = 10) | ||||
| γ-SNAP | 34.7 × 103 | 1.7 ± 0.55 | 2,950 | 0.54 |
| (n = 7) |
| Protein . | Calculated MW* (g/mol) . | ng/107 Cells . | Molecules/cell . | Concentration (μmol/L)† . |
|---|---|---|---|---|
| NSF | 247.9 × 103‡ | 7.0 ± 1.3 | 1,700 | 0.32 |
| (nρ = 11) | ||||
| α-SNAP | 33.2 × 103 | 3.1 ± 0.66 | 5,600 | 1.0 |
| (n = 10) | ||||
| γ-SNAP | 34.7 × 103 | 1.7 ± 0.55 | 2,950 | 0.54 |
| (n = 7) |
Cells were counted by hemocytometer and were solubilized in SDS-sample buffer before SDS-PAGE and Western blotting. The antigens were detected by chemiluminescence and the images were quantified by digital scanning (see Materials and Methods for details). Integration of the platelet proteins were compared with that of a standard curve of recombinant proteins to determine the amount of antigen per platelet.
Molecular weights were calculated based on the amino acid sequences.
The volume of a platelet taken from literature values was 9 fL.54 55
The calculated molecular weight for a homo-trimeric NSF of 82.6 × 103 g/mol subunits.
ρ Represents the number of independent measurements made.