C.D.Atreya, K.V.Mohan, OVRR, CBER, FDA, Rockville MD
The function of a protein is intimately associated with its subcellular localization, which is a signal-dependent event. Signals for targeting cellular proteins to the endoplasmic reticulum, mitochondria, nucleus or the cell membrane have already been identified and the most recent inclusion to this list of organelle-targeting signals is the peroxisomal targeting signal (PTS). Peroxisomes are vital cellular organelles controlling important metabolic functions like hydrogen peroxide degradation, fatty acid metabolism, gluconeogenesis, toxin degradation, etc. Certain human metabolic disorders such as Zellweger syndrome, neonatal adrenoleukodystrophy, infantile Refsum disease and rhizomelic chondrodysplasia punctata are associated with the peroxisomal defect in protein import and/ or biogenesis. The peroxisomal targeting signals are of two types, PTS1 and PTS2. Type 1 signal sequence is a tripeptide motif present near or at the carboxy terminal of the protein whereas, PTS2 constitutes a combination of nine amino acid bipartite sequence in the N-terminal half of the protein. Proteins from mammals, plants, fungi, parasites have all been identified to contain PTS. However, so far these signals have not been reported among viral proteins. We report here the identification and conservation of both PTS1 and PTS2 among a variety of viral proteins.