NaV1.7 is a voltage-gated sodium ion channel implicated by human genetic evidence as a therapeutic target for the treatment of pain. Screening fractionated venom from the tarantula Grammostola porteri led to the identification of a 34-residue peptide, termed GpTx-1, with potent activity on NaV1.7 (IC50 = 10 nM) and promising selectivity against key NaV subtypes (20× and 1000× over NaV1.4 and NaV1.5, respectively). NMR structural analysis of the chemically synthesized three disulfide peptide was consistent with an inhibitory cystine knot motif. Alanine scanning of GpTx-1 revealed that residues Trp(29), Lys(31), and Phe(34) near the C-terminus are critical for potent NaV1.7 antagonist activity. Substitution of Ala for Phe at position 5 conferred 300-fold selectivity against NaV1.4. A structure-guided campaign afforded additive improvements in potency and NaV subtype selectivity, culminating in the design of [Ala5,Phe6,Leu26,Arg28]GpTx-1 with a NaV1.7 IC50 value of 1.6 nM and >1000× selectivity against NaV1.4 and NaV1.5.

The tremendous challenge of inhibiting therapeutically important protein–protein interactions has created the opportunity to extend traditional medicinal chemistry to a new class of targets and to explore nontraditional strategies. Here we review a widely studied system, the interaction between tumor suppressor p53 and its natural antagonist MDM2, for which both traditional and nontraditional approaches have been reported. This system has been a testing ground for novel proteomimetic scaffold‐based strategies, i.e., for attempts to mimic the recognition surface displayed by a folded protein with unnatural oligomers. Retroinverso peptides, peptoids, terphenyls, β‐hairpins, p‐oligobenzamides, β‐peptides, and miniproteins have all been explored as inhibitors of the p53/MDM2 interaction, and we focus on these oligomer‐based efforts. Traditional approaches have been successful as well, and we briefly review small molecule inhibitors along with other strategies for reactivation of the p53 pathway, for comparison with oligomer‐ based approaches. We close with comments on an emerging dichotomy among protein–protein interaction targets. © 2007 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 88: 657–686, 2007.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

[structure: see text] We have evaluated the effects of microwave irradiation on the solid-phase synthesis of beta-peptides. Sequences designed to adopt the 14-helix, especially those containing the structure-promoting residue trans-2-aminocyclohexanecarboxylic acid (ACHC), suffer from poor synthetic efficiency under standard SPPS conditions. A comparison of microwave and conventional heating shows that both provide excellent synthetic results for shorter sequences; however, we identify a clear benefit from microwave irradiation for longer beta-peptides.

There is interest in the identification and optimization of new molecular entities selectively targeting ion channels of therapeutic relevance. Peptide toxins represent a rich source of pharmacology for ion channels, and we recently reported GpTx-1 analogs that inhibit NaV1.7, a voltage-gated sodium ion channel that is a compelling target for improved treatment of pain. Here we utilize multi-attribute positional scan (MAPS) analoging, combining high-throughput synthesis and electrophysiology, to interrogate the interaction of GpTx-1 with NaV1.7 and related NaV subtypes. After one round of MAPS analoging, we found novel substitutions at multiple residue positions not previously identified, specifically glutamic acid at positions 10 or 11 or lysine at position 18, that produce peptides with single digit nanomolar potency on NaV1.7 and 500-fold selectivity against off-target sodium channels. Docking studies with a NaV1.7 homology model and peptide NMR structure generated a model consistent with the key potency and selectivity modifications mapped in this work.

Protein-protein interactions play crucial roles in cell-signaling events and are often implicated in human disease. Molecules that bind tightly to functional protein-surface sites and show high stability to degradative enzymes could be valuable pharmacological tools for dissection of cell-signaling networks and might ultimately lead to therapeutic agents. We recently described oligomers containing both alpha- and beta-amino acid residues that bind tightly to the BH3 recognition site of the anti-apoptotic protein Bcl-x(L). The oligomers with highest affinity had a nine-residue N-terminal segment with a 1:1 alpha:beta residue repeat and a six-residue C-terminal segment containing exclusively proteinogenic alpha-residues. The N-terminal portions of such (alpha/beta+alpha)-peptides are highly resistant to proteolysis, but the C-terminal alpha-segments are susceptible. This study emerged from efforts to modify the alpha-segment in an (alpha/beta+alpha)-peptide in a way that would diminish proteolytic degradation but retain high affinity for Bcl-x(L). Some of the oligomers reported here could prove useful in certain biological applications, particularly those for which extended incubation in a biological milieu is required.