UniProt release 5.2
Published June 7, 2005
Uncleaved N-terminal translocation signals
The translocation of a protein to another subcellular compartment requires the existence of at least one translocation signal specific to the relevant trafficking mechanism across the membrane. Proteins destined for secretion, incorporation into the plasma membrane, chloroplast, cyanelle, microbodies or the mitochondrial matrix usually possess an N-terminal transfer signal, which is cleaved during the transfer process. Recently, some proteins have been found to obviously get around this cleavage step. In some cases, the uncleaved signal peptide even confers important functional properties to the protein (P27169).
In the current Swiss-Prot release, the annotation of 23 protein entries indicates an uncleaved signal sequence (e.g. O95445) and the transit peptide of the mitochondrial 3-ketoacyl-CoA thiolase was reported to be not removed (P42765).