Practice question

Proving internal mitochondrial localization requires protease protection assay combined with protein detection that provides molecular weight information. Isolated mitochondria are treated with proteinase K; outer membrane proteins degrade while matrix and inner membrane proteins protected by intact membranes remain. After lysis, samples resolved by SDS-PAGE and probed immunologically confirm persistence of target. Reverse transcription PCR measures RNA absent after protease treatment assessment, Southern detects DNA, and ELISA quantifies without size verification, unable to distinguish truncated degradation products. Therefore immunoblotting furnishes essential evidence of import and protected full-length protein inside organelle.