Proteins coded for by nuclear DNA but found within mitochondria move from the cytoplasm into mitochondria using signal sequence.
Protein targeting or sorting is a process by which synthesized proteins are transported to their appropriate localizations in the cell or outside it. Proteins can be targeted to the inner space of an organelle (such as Golgi apparatus, endoplasmic reticulum or mitochondria) or its membrane, plasma membrane, or to exterior of the cell via secretion.
Usually, protein contains signal sequence on the N terminus that is involved in destination targeting.
