Signal peptidase

Signal peptidases were initially observed in endoplasmic reticulum (ER)-derived membrane fractions isolated from mouse myeloma cells.

[1] The key observation by César Milstein and colleagues was that immunoglobulin light chains were produced in a higher molecular weight form, which became processed by the ER membrane fraction.

[2] Signal peptidases are also found in prokaryotes as well as the protein import machinery of mitochondria and chloroplasts.

Sec11 is the only essential factor for signal peptide processing as can be deduced from a growth defect upon its deletion.

[6] The SPC structure suggests that the enzyme has a transmembrane domain that is only accessible to signal peptides with their characteristically short helical segment.