Peptides as Disruptors of Protein Protein Interactions

Peptides mimicking binding domains disrupt protein-protein interactions with high selectivity by competitively binding to one of the interacting partners. Such peptides have been widely utilized to gain insight into the function of protein-protein interactions (Shin et al. 2005).

The generation of disruptor peptides requires mapping of the interacting domains. Recent studies took advantage of a combination of peptide spot technology (Kramer and Schneider-Mergener 1998; Frank 2002) and overlay assays with recombinant proteins (Kofler et al. 2005; Hundsrucker et al. 2006; Stefan et al. 2007; Sachs et al. 2007; Baillie et al. 2007). Here, overlapping peptides of up to 27 amino acids in length covering the entire sequence of a protein are spot-synthesized on cellulose membranes and overlaid with a potential interacting partner. This, together with analysis of 3D protein structures, reveals continuous and discontinuous interaction sites (Bolger et al. 2006). The influence of single amino acid contributions to the interaction is revealed by amino acid substitution arrays in which every amino acid is replaced with every amino acid found in native proteins (an example is shown in Fig. 1). This approach allows for optimisation of peptides, i.e., an increase in affinity and selectivity (Burns-Hamuro et al. 2003; Gold et al. 2006). Interactions detected by this technique need to be confirmed by other approaches, e.g., immunoprecipitation studies with truncated versions of the proteins.

Optimised peptides to be used for disruption of protein-protein interactions can be modified for visualisation, immobilisation or cell permeation by coupling to fluorescent dyes, affinity tags, cell penetrating tags or sequences (e.g., stearate, poly-arginine, penetratin, MAP- or Tat-peptide), respectively, (Vives, 2005; Zorko and Langel 2005; Lygren et al. 2007; Smith et al. 2007).

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