Phalloidin Synthetic Analogues: Structural Requirements in the Interaction with F-Actin

Abstract

Synthetic derivatives of phalloidin have been investigated in solution by circular dichroism (CD) and NMR spectroscopy. They differ from natural phalloidin (PHD), bicyclo(Ala 1 -d-Thr 2 -Cys 3 -cis-4-hydroxy-Pro 4 -Ala 5 -2-mercapto-Trp 6 -(OH) 2 Leu 7 )(S-3 3 6), in that they are modified at positions 2, 3, and 7. Among these synthetic analogues, structural differences and varying degrees of atropisomerism are found. By comparing the respective molecular models obtained by restrained molecular dynamics (RMD) simulations based on experimental NMR data, structural features that may be responsible for the different biological behavior become apparent. Our results indicate that the structural changes that result from an inversion of chirality of residue 3 lead to a complete loss of toxicity. Conversely, toxicity is less affected by the structural changes that stem from an inversion of chirality of residue 2. Moreover, unlike the other phallotoxins, when the thioether unit bridges to the opposite face of the main peptide ring, in contrast to the situation in other phallotoxins, large structural changes are observed as well as a total loss of activity. Molecular models of the synthetic phalloidin analogues have been used to investigate the necessary structural requirements for the interaction with F-actin. To this end, the F-actin/PHD model of M. Lorenz et al. was employed; docking experiments of our molecular models in the PHD binding site are presented.

Hydrogen/Deuterium Exchange Mass Spectrometry of Actin in Various Biochemical Contexts

“…Molecular modeling suggests a possible interaction between phalloidin and Y281 on the N þ 2 monomer, which would fall in fragment 1853.84. 33 No change in deuteration was observed for the N þ 2 monomer in the region around phalloidin ( Figure 5). This could be due to a small gap in the coverage in this region (K286-C287).…”

Structural effects and functional implications of phalloidin and jasplakinolide binding to actin filaments

“…Furthermore, both molecules 210 contain an indole group that occupies the same hydrophobic pocket. This indole group has been 211 proposed to be of great importance for phalloidin binding and was shown 212 to be essential for its toxicity (Falcigno et al, 2001;T. Wieland, 1977).…”

Tuning a Polar Molecule for Selective Cytoplasmic Delivery by a pH (Low) Insertion Peptide

“…According to the literature (18, 21, 22) it was expected that modification of COOH group of phallacidin should not affect F-actin binding properties. Phallatoxin binds between actin monomers in filamentous actin and prevents depolymerization (19, 21).…”