Probing essential residues for cellular uptake with a cationic nuclear localization signal sequence.

The nuclear localization signal sequence (NLS) of the transcription factor NF- κB is a cationic peptide with the ability to cross the cytoplasmic membrane and facilitate the delivery of attached cargo, such as DNA and proteins, to cells. Previous research had pointed to the essential role of cationic residues, therefore, the importance of residues within the NLS of NF- κB was evaluated for cellular uptake using an alanine replacement strategy. Although it was expected that removal of the cationic groups would have the greatest effect on membrane translocation, the most significant decreases in cellular uptake occurred with the replacement of the hydrophilic Q6 (80%) and the hydrophobic L8 (70%) residues. Replacement of the positively charged residues resulted in 30–40% decrease in cellular uptake, indicating that electrostatic interactions are not the primary driving force for membrane translocation. [ABSTRACT FROM AUTHOR]