1. Peptaibol antiamoebin I: spatial structure, backbone dynamics, interaction with bicelles and lipid-protein nanodiscs, and pore formation in context of barrel-stave model
Zakhar O Shenkarev, et al. Chem Biodivers. 2013 May;10(5):838-63. doi: 10.1002/cbdv.201200421.
Antiamoebin I (Aam-I) is a membrane-active peptaibol antibiotic isolated from fungal species belonging to the genera Cephalosporium, Emericellopsis, Gliocladium, and Stilbella. In comparison with other 16-amino acid-residue peptaibols, e.g., zervamicin IIB (Zrv-IIB), Aam-I possesses relatively weak biological and channel-forming activities. In MeOH solution, Aam-I demonstrates fast cooperative transitions between right-handed and left-handed helical conformation of the N-terminal (1-8) region. We studied Aam-I spatial structure and backbone dynamics in the membrane-mimicking environment (DMPC/DHPC bicelles)(1) ) by heteronuclear (1) H,(13) C,(15) N-NMR spectroscopy. Interaction with the bicelles stabilizes the Aam-I right-handed helical conformation retaining significant intramolecular mobility on the ms-μs time scale. Extensive ms-μs dynamics were also detected in the DPC and DHPC micelles and DOPG nanodiscs. In contrast, Zrv-IIB in the DPC micelles demonstrates appreciably lesser mobility on the μs-ms time scale. Titration with Mn(2+) and 16-doxylstearate paramagnetic probes revealed Aam-I binding to the bicelle surface with the N-terminus slightly immersed into hydrocarbon region. Fluctuations of the Aam-I helix between surface-bound and transmembrane (TM) state were observed in the nanodisc membranes formed from the short-chain (diC12 : 0) DLPC/DLPG lipids. All the obtained experimental data are in agreement with the barrel-stave model of TM pore formation, similarly to the mechanism proposed for Zrv-IIB and other peptaibols. The observed extensive intramolecular dynamics explains the relatively low activity of Aam-I.
2. [Molecular dynamics of zervamicin II and its analogues in water and methanol]
O V Levtsova, M Iu Antonov, A K Shaĭtan, I A Orshanskiĭ, I N Nikolaev, K V Shaĭtan Biofizika. 2009 Jul-Aug;54(4):616-21.
A comparative study of the molecular dynamics of zervamicin II (an antimicrobial peptide from the peptaibol group, which has the channel-forming activity) in water and methanol has been performed. The influence of amino acid substitutions on the dynamics and stability of the peptide structure has been investigated. The amino acid sequence responsible for the absence of swivel motions in short peptaibols has been determined.
3. Modeling of peptaibol analogues incorporating nonpolar α,α-dialkyl glycines shows improved α-helical preorganization and spontaneous membrane permeation
Tarsila G Castro, Nuno M Micaêlo J Phys Chem B. 2014 Jan 23;118(3):649-58. doi: 10.1021/jp4074587. Epub 2014 Jan 13.
In this study, we investigate the effect of nine noncanonical α,α-dialkyl glycines on the structure, dynamics, and membrane permeation properties of a small peptaibol, peptaibolin. The noncanonical amino acids under study are Aib (α-amino isobutyric acid), Deg (α,α-diethyl glycine), Dpg (α,α-dipropyl glycine), Dibg (α,α-di-isobutyl glycine), Dhg (α,α-dihexyl glycine), DΦg (α,α-diphenyl glycine), Db(z)g (α,α-dibenzyl glycine), Ac6c (α,α-cyclohexyl glycine), and Dmg (α,α-dihydroxymethyl glycine). It is hypothesized that these amino acids are able to induce well-defined secondary structures in peptidomimetics. To investigate this hypothesis, we designed new peptaibolin peptidomimetics by replacing the native Aib positions with a new α,α-dialkyl glycine. We show that Dhg and Ac6c noncanonical amino acids are able to induce α-helix secondary structures of peptaibolin in water, which are not present in the native structure. We also demonstrate that the α,α-dialkyl glycines increase the membrane permeability of peptaibolin in 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) membranes. However, there is no apparent correlation between increased helicity and membrane permeability. In summary, we show that some α,α-dialkyl glycines under study induce the formation of α-helix secondary structures in peptaibolin and promote spontaneous membrane permeation. Our findings increase the knowledge of the membrane permeability and folding of peptides incorporating α,α-dialkyl glycines.
