PTS1signaali

PTS1signaali refers to the peroxisomal targeting signal type 1. This is a specific amino acid sequence found at the C-terminus of many peroxisomal matrix proteins. The most common and well-studied PTS1 is the tripeptide sequence Ser-Lys-Leu (SKL). However, variations exist, and other sequences can also function as PTS1 signals. The presence of a functional PTS1 is crucial for the correct localization of these proteins to the peroxisome lumen.

The PTS1 signal is recognized by a specific receptor protein called peroxisomal targeting signal receptor (PTS1R), also known as PEX5. PEX5 is a soluble protein that binds to the PTS1 sequence on a cargo protein in the cytosol. This PEX5-cargo complex then docks with the peroxisomal membrane, mediated by other proteins known as peroxins. Through a process that is not fully understood, the cargo protein is translocated across the peroxisomal membrane into the lumen, while PEX5 is recycled back to the cytosol.

Without a functional PTS1 signal, or if the PTS1 receptor is defective, proteins destined for the peroxisome lumen will remain in the cytosol or be mislocalized to other cellular compartments. This mislocalization can lead to various cellular dysfunctions and is associated with a class of inherited disorders known as peroxisome biogenesis disorders. The study of PTS1 and its receptor system has provided significant insights into protein import and targeting mechanisms within eukaryotic cells.