Submitochondrial localization of human OGG1 proteins, determined by electron microscopic immunocytochemistry. After each mitochondria was isolated from MR-2a:HA (A), MR-ΔN31:HA (B), and MR-V cells (C), thin sections (∼0.1 μm) were prepared for electron microscopic immunocytochemistry with anti–2a-CT in combination with protein A–gold. Anti–2a-CT preabsorbed with TrpE-2a-CT–Sepharose was applied to mitochondria from MR-V cells (D). Bars, 0.2 μm.