Signaalisarja

Signaalisarja, also known as a signal sequence, is a specific pattern of amino acids found at the N-terminus (the amino end) of certain proteins. This sequence serves as a signal for the protein to be transported to its correct location within the cell or to be secreted outside the cell. The most well-known signal sequence is the N-terminal signal peptide, which is typically 15-30 amino acids long and is recognized by the signal recognition particle (SRP) in the endoplasmic reticulum (ER) during protein synthesis.

The signal sequence can be classified into several types based on its function. For example, the classical signal sequence is found in secretory proteins and is recognized by the SRP, which targets the protein to the ER for further processing and secretion. Other types of signal sequences include the mitochondrial targeting sequence, which directs proteins to the mitochondria, and the nuclear localization signal, which targets proteins to the nucleus.

The signal sequence is usually removed from the mature protein after it has been transported to its correct location. In the case of secretory proteins, the signal sequence is cleaved off by signal peptidases in the ER, and the remaining protein is then transported through the ER and the Golgi apparatus before being secreted from the cell.

Signaalisarja plays a crucial role in protein trafficking and localization within the cell, ensuring that proteins are directed to their correct destinations and can perform their specific functions.