6dst
Recombinant melittinRecombinant melittin
Structural highlights
FunctionMEL_APIME Melittin: Main toxin of bee venom with strong hemolytic activity. Forms a pore in the cell membrane by inserting into lipid bilayers in an alpha-helical conformation and has multiple effects, probably, as a result of its interaction with negatively charged phospholipids. It inhibits well known transport pumps such as the Na(+)-K(+)-ATPase and the H(+)-K(+)-ATPase. It increases the permeability of cell membranes to ions, particularly Na(+) and indirectly Ca(2+), because of the Na(+)-Ca(2+)-exchange. It acts synergistically with phospholipase A2.[1] Melittin-S: 1.4-fold less hemolytic and adopts a less organized secondary structure than melittin.[2] Publication Abstract from PubMedMelittin is an extensively studied, 26-residue toxic peptide from honey-bee venom. Because of its versatility in adopting a variety of secondary (helix or coil), and quaternary (monomer or tetramer) structures in various environments, melittin has been the focus of numerous investigations as a model peptide in protein folding studies, as well as in studies involving binding to proteins, lipids and polysaccharides. A significant body of evidence supports the view that melittin binds to these macromolecules in a predominantly helical conformation, but detailed structural knowledge of this conformation is lacking. In this report, we present nuclear magnetic resonance (NMR)-based structural insights into the helix formation of recombinant melittin in the presence of TFE - a known secondary structure inducer in peptides. These studies were performed at neutral pH, with micromolar amounts of the peptide. Using Nuclear Overhauser effect (NOE)-derived distance restraints from 3D NMR spectra, we determined the atomic resolution NMR solution structure of recombinant melittin bearing a TFE-stabilized helix. To circumvent the complications with structure determination of small peptides with high conformational flexibility, we developed a workflow for enhancing proton NOEs by increasing the viscosity of the medium. In the TFE-containing medium, recombinant monomeric melittin forms a long, continuous helical structure, which consists of the N-and C-terminal alpha-helices and the non-canonical 310-helix in the middle. The non-canonical 310-helix is missing in the previously solved X-ray structure of tetrameric melittin and the NMR structure of melittin in methanol. Melittin's structure in TFE containing medium provides insights into melittin's conformational transitions, which are relevant to the peptide's interactions with its biological targets. Helical Structure of Recombinant Melittin.,Ramirez LS, Pande J, Shekhtman A J Phys Chem B. 2018 Dec 20. doi: 10.1021/acs.jpcb.8b08424. PMID:30570258[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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