Nuclear localisation signals

• nuclear localisation signals are responsible for the selectivity of active nuclear import process
• most common signal is 1/2 short sequences rich in amino acids (lysine + arginine which have positive charge)
• they can be located almost anywhere in the amino acid sequence and forms loops/patches on the protein surface
• many NLS function even when linked as short peptides to the surface of a cytosolic protein.

  the precise location of signal within the amino acid sequence is not important
• if one of the protein subunits of a multicomponent complex displays a NLS, the entire complex will be imported into the nucleus.
• NPC transport occurs via large, constitutively open mesh-filled pores.

  these are fully folded proteins and large multi protein complexes that can be transported in either directions via nuclear pore.