TABLE 2.
Assessment of the stoichiometry of Tom proteinsa
| Component or structure | Abundance, pmol/mg of mitochondrial protein (associated with GIP complex) |
|---|---|
| Tom proteins | |
| Tom20 | 60–70 (4–12) |
| Tom22 | 200–300 (200–300) |
| Tom40 | 250–300 (250–300) |
| Tom70 | 60–70 (<3) |
| GIP complexes | 45–60 |
| Translocation contact sites | 15 |
| Tim core complexes | 15–20 |
a
The abundance of Tom proteins was determined by standardized immunoblotting with expressed and purified protein cytosolic domains (6, 9) and antibodies generated against them. The reactivities of the antibodies with the SDS-denatured proteins were compared for the purified proteins and the mitochondrial extracts. The data for the abundance of GIP complexes, translocation contact sites, and Tim core complexes and the 250-pmol/mg value for Tom40 are derived from reference 9. The association with the GIP complex was determined by blue native gel electrophoresis and coimmunoprecipitation.