Verified Translation Starts Sites

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A subset of the Verified Set confirm the start codon of translation for cytoplasmic and inner membrane proteins because there is no signal peptide cleaved. This subset is further divided into proteins in which the N-terminal methionine is clipped off by methionine amino peptidase (MAP), or is not clipped by MAP.


Non-secreted proteins may be processed by methionine amino peptidase (MAP) to remove the terminal methionine, depending on the size of the second amino acid. The N-termini must be deformylated by Def before Map can act. Sometimes the second amino acid is small and MAP could act, but apparently does not, perhaps due to sequesterization of the N-terminus in the inner membrane before Def or MAP can act on it. MAP is not present in cells in large excess and overexpressed proteins may not all get processed by MAP or Def.