Characterization of Hydroxyproline-Containing Hairpin-Like Antimicrobial Peptide EcAMP1-Hyp from Barnyard Grass (Echinochloa crusgalli L.) Seeds: Structural Identification and Comparative Analysis of Antifungal Activity.

Herein, we describe a modified form of the antimicrobial hairpin-like peptide EcAMP1, isolated from barnyard grass (E. crusgalli) seeds, which is structurally characterized by a combination of high-pressure liquid chromatography, mass spectrometry, and automated Edman sequencing. This derivate has a single amino acid substitution (Pro19Hyp) in the second α-helical region of the molecule, which is critical for the formation of the hydrophobic core and the secondary structure elements. Comparing the antifungal activity of these two peptides, we found that the modified EcAMP1-Hyp had a significantly weaker activity towards the most-sensitive plant pathogenic fungus Fusarium solani. Molecular dynamics simulations and in vitro binding to the commercial polysaccharides allowed us to conclude that the Pro-19 residue is important for binding to carbohydrates located in the spore cell wall and it chiefly exhibits a fungistatic action representing the hyphal growth inhibition. These data are novel and significant for understanding a role of α-hairpinins in plant immunity.

Characterization of HIV-1 integrase interaction with human Ku70 protein and initial implications for drug targeting.

Human Ku70/Ku80 protein is known to influence HIV-1 replication. One of the possible reasons may be the protection of integrase from proteasomal degradation by Ku70 subunit. We demonstrated that recombinant HIV-1 integrase and Ku70 form a stable complex, while no interaction of Ku70 with integrase from prototype foamy virus was observed. By analyzing protein subdomains we determined two binding sites in the structure of both Ku70 and integrase: the 51-160 a.a. region of integrase interacts with residues 251-438 of Ku70, whereas Ku70 N-terminal domain (1-250 a.a.) contacts an α6-helix in the 200-220 a.a. integrase region. Single substitutions within integrase (E212A or L213A) block the interaction with Ku70 thus indicating that the binding site formed by the 200-220 a.a. integrase region is crucial for complex formation. E212A/L213A substitutions decreased the integrase capacity to bind Ku70 in HEK293T cells. A conjugate of 2'-ОMe-GGUUUUUGUGU oligonucleotide with eosin is shown by molecular modeling to shield integrase residues E212/L213 and is effective in blocking complex formation of Ku70 with integrase what makes the complex between α6-helix and Ku70(1-250) a possible target for drug development.