Cellular interacting proteins of functional screen-derived antiproliferative and cytotoxic peptides discovered using shotgun peptide sequencing.

Abstract Three nuclear-excluded antiproliferative peptides discovered in an intracellular peptide library screen contained variants of a leucine-rich nuclear exclusion motif. When tagged with N-terminal lys 7 , two peptides, but not quadruple alanine motif mutants, killed A549 cells. Cellular proteins bound to N-biotinylated analogs, but not to biotinylated inactive mutants, included a set of proteins involved in nucleocytoplasmic transport, including exportin-1, importin β subunits, importin α, nucleoporin p62, and the GTPase ran. The peptides, but not mutants, also bound other protein sets including tubulin and actin, elongation factors, mRNA-associated splicing factors, and proteins associated with DNA replication such as PCNA, annexin II, and calpactin. Many extracted proteins are linked to nucleocytoplasmic transport, and some are involved in cell cycle regulation. These peptides may act by disrupting nucleocytoplasmic transport of proteins important for cell growth.