Table 2.

Eukaryotic Protein targeting domains with positional requirements

Sequence Position	Localization	Notes
NH2 terminal domains
Signal Sequence-	ER	Usually posttranslationally cleaved
Presequence-	Mitochondria	Amphipathic helix that is usually posttranslationally cleaved
Myristoylation Sequence	Cytoplasmic face of cellular membranes	Initiating methionine is cleaved
COOH terminal domains
-KDEL	ER retrieval motif for luminal proteins	Domain must be in the ER lumen.
-KKXX (X is any amino acid)	ER retrieval motif for integral membrane proteins	Domain must be exposed in the cytoplasm
-SKL	Peroxisome lumen
-GPI Anchor Sequence	Binds luminal and extracellular leaflets of cellular membranes	Fragment of COOH terminus of protein is cleaved for fusion with GPI
-Tail Anchor	ER or mitochondrial membrane
-CAAX (X is any amino acid)	palmitoylation