The role of hydrophobic patches of de novo designed MSI-78 and VG16KRKP antimicrobial peptides on fragmenting model bilayer membranes

Antimicrobial peptides (AMPs) with cell membrane lysing capability are considered potential candidates for the development of the next generation of antibiotics. Designing novel AMPs requires an in-depth understanding of the mechanism of action of the peptides. In this work, we used various biophysical techniques including ³¹P solid-state NMR to examine the interaction of model membranes with amphipathic de novo-designed peptides. Two such peptides, MSI-78 and VG16KRKP, were designed with different hydrophobicity and positive charges. The model lipid membranes were constituted by mixing lipids of varying degrees of 'area per lipid' (APL), which directly affected the packing properties of the membrane. The observed emergence of the isotropic peak in ³¹P NMR spectra as a function of time is a consequence of the fragmentation of the membrane mediated by the peptide interaction. The factors such as the charges, overall hydrophilicity of the AMPs, as well as lipid membrane packing, contributed to the kinetics of membrane fragmentation. Furthermore, we anticipate the designed AMPs follow the carpet and toroidal pore mechanisms when lysing the cell membrane. This study highlights the significance of the effect of the overall charges and the hydrophobicity of the novel AMPs designed for antimicrobial activity.

Effects and mechanism of gating modifier spider toxins on the hERG channel

Jingzhaotoxin-I, -III, -IV, -XIII, and -35 (JZTX-I, -III, -IV, -XIII, and -35), gating modifier toxins isolated from the venom of the Chinese tarantula Chilobrachys Jingzhao, were reported to act on cardiac sodium channels and Kv channels. JZTX-I and JZTX-XIII inhibited the hERG channel with the IC₅₀ value of 626.9 nM and 612.6 nM, respectively. JZTX-III, -IV, and -35 share high sequence similarity with JZTX-I and JZTX-XIII, but they showed much lower affinity on the hERG channel compared with JZTX-I and JZTX-XIII. The inhibitory potency of the above five toxins on the hERG channel was not in accordance with their affinity on the Nav1.5 and Kv2.1 channels, indicating that the bioactive surfaces of the five toxins interacting with hERG, Nav1.5 and Kv2.1 are at least in part different. Structure-function analysis of the gating modifier toxins suggested that the functional bioactive surface binding to the hERG channel consists of a conserved hydrophobic patch, surrounding acidic residues (Glu10 in JZTX-XIII, Glu11 in JZTX-I), and basic residues which may be different from residues binding to the Kv2.1 channel.

Contribution of the gp120 V3 loop to envelope glycoprotein trimer stability in primate immunodeficiency viruses

The V3 loop of the human immunodeficiency virus type 1 (HIV-1) gp120 exterior envelope glycoprotein (Env) becomes exposed after CD4 binding and contacts the coreceptor to mediate viral entry. Prior to CD4 engagement, a hydrophobic patch located at the tip of the V3 loop stabilizes the non-covalent association of gp120 with the Env trimer of HIV-1 subtype B strains. Here, we show that this conserved hydrophobic patch (amino acid residues 307, 309 and 317) contributes to gp120-trimer association in HIV-1 subtype C, HIV-2 and SIV. Changes that reduced the hydrophobicity of these V3 residues resulted in increased gp120 shedding and decreased Env-mediated cell-cell fusion and virus entry in the different primate immunodeficiency viruses tested. Thus, the hydrophobic patch is an evolutionarily conserved element in the tip of the gp120 V3 loop that plays an essential role in maintaining the stability of the pre-triggered Env trimer in diverse primate immunodeficiency viruses.

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The V3-loop of HIV-1 gp120 contributes to Env trimer stability and viral entry.

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The hydrophobic patch in the tip of the V3 loop is critical for pre-triggered Env trimer stability.

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The hydrophobic patch is a conserved motif in primate immunodeficiency viruses.