35 kDa PGC-1α localizes to the mitochondrial inner membrane and the matrix. A) Purified mitochondria from the mouse hippocampus were treated with protease K (lane 1), treated with trypsin (lane 2), or left untreated (lane 3). The amount of PGC-1α, VDAC, NDUFV2, Histone H3, or GAPDH was determined by Western blotting. B) Western blot analysis of mitochondrial inner membrane (Mem) and matrix (Sol.) probed with antibodies directed against P-120, NDUFV2, Grp 75, Histone H3 (a nuclear marker), and GAPDH (a cytosolic marker). Immunoelectron microscopy of mouse hippocampus tissue with P-120 antibody (C), followed by OsO4 treatment (D), or without P-120 antibody (E). Arrows indicate PGC-1α Immunogold labeling.