Peptidomimetics in cancer chemotherapy

Targeting protein-protein interactions (PPIs) of transcription factors: Challenges of intrinsically disordered proteins (IDPs) and regions (IDRs)

In this review we discuss recent progress in targeting the protein-protein interactions made by oncogenic transcription factors. We particularly focus on the challenges posed by the prevalence of intrinsically disordered regions in this class of protein and the strategies being used to overcome them.

Exploring novel strategies for AIDS protozoal pathogens: α-helix mimetics targeting a key allosteric protein-protein interaction in C. hominis TS-DHFR

The bifunctional enzyme thymidylate synthase-dihydrofolate reductase (TS-DHFR) from the protozoal parasite Cryptosporidium hominis is a potential molecular target for the design of antiparasitic therapies for AIDS-related opportunistic infections. The enzyme exists as a homodimer with each monomer containing a unique swap domain known as a "crossover helix" that binds in a cleft on the adjacent DHFR active site. This crossover helix is absent in species containing monofunctional forms of DHFR such as human. An in-depth understanding of protein-protein interactions between the crossover helix and adjacent DHFR active site that might modulate enzyme integrity or function would allow for insights into rational design of species-specific allosteric inhibitors. Mutational analysis coupled with structural studies and biophysical and kinetic characterization of crossover helix mutants identifies this domain as essential for full enzyme stability and catalytic activity, and pinpoints these effects to distinct faces of the crossover helix important in protein-protein interactions. Moreover, targeting this helical protein interaction with α-helix mimetics of the crossover helix leads to selective inhibition and destabilization of the C. hominis TS-DHFR enzyme, thus validating this region as a new avenue to explore for species-specific inhibitor design.

Bioavailability of insect neuropeptides: the PK/PBAN family as a case study

The ability of unmodified linear peptides to penetrate the insect cuticle and exert bioactivity (e.g., stimulation of sex pheromone biosynthesis) was tested by topical application onto Heliothis peltigera moths of four insect neuropeptides (Nps) of the pyrokinin (PK)/pheromone biosynthesis activating neuropeptide (PBAN) family: Helicoverpa zea PBAN (Hez-PBAN), Pseudaletia (Mythimna) separata pheromonotropin (PT), Leucophaea maderae PK (LPK) and Locusta migratoria myotropin (Lom-MT-II). The time kinetic of the peptides applied in double distilled water (DDW) or dimethylsulfoxide (DMSO) was tested and the activities of topically applied and injected peptides were compared. The results clearly indicated that all four peptides were highly potent but with differing activities in the two solvents: PBAN was most active in water, and PT in DMSO. The activity of PBAN in DDW lasted up to 8h post-application and its activity in this solvent showed a faster onset and a longer persistence than in DMSO. LPK and MT differed less in their kinetics between the two solvents. Topically applied PBAN at 1 nmol exhibited an equivalent or even significantly higher potency than the injected peptide at several different times post-treatment. Similar results were obtained with topically applied and injected LPK. The present results add important information on the bioavailability of unmodified linear peptides in moths, clearly indicate that linear hydrophilic peptides can penetrate the cuticle by contact application in aqueous solutions and in organic solvents very efficiently, reach their target organ and activate it.

Synthesis of P,N-heterocycles from omega-amino-H-phosphinates: conformationally restricted alpha-amino acid analogs

P,N-heterocycles (3-hydroxy-1,3-azaphospholane and 3-hydroxy-1,3-azaphosphorinane-3-oxide) are synthesized in moderate yield from readily available omega-amino-H-phosphinates and aldehydes or ketones via an intramolecular Kabachnik-Fields reaction. The products are conformationally restricted phosphinic analogs of alpha-amino acids. The multigram-scale syntheses of the H2N(CH2)(n)PO2H2 phosphinic precursors (n = 1, 2, 3) and some derivatives are also described.