When a bee stings you, it leaves its stinger within your body releasing a peptide toxin called melittin. Melittin is toxic to cells because it is able to insert and bind to the cell membrane, which destabilizes the membrane.
Melittin is able to interact with the hydrophobic lipid layer of the cell membrane by forming unique helixes where hydrogen bonding occurs between both peptides. Consequently, charged (polar) amino acid residues are generally not observed in such proteins and pH can change the binding affinity. Such proteins are called membrane active proteins (MAPs).
Now this is not good for your bee-stung cells, but researchers are looking to repurpose nature’s disruptive proteins as anti-microbial drugs, cancer therapeutics, and HIV drugs. Specifically, researchers in the Kalina Hristova lab in the Department of Materials Science and Engineering at Johns Hopkins are engineering proteins based off of the melittin protein.
The Hristova lab researchers study their developed MAPs by using lab-produced vesicles from phosphatidylcholine (the major component of a cell membrane). They use the natural fluorescence from tryptophan (which increases in a hydrophobic environment), and circular dichroism spectroscopy (which is able to detect the chiral structure of proteins) to verify the peptide’s interactions with the vesicles, and what affinity they will bind.
About the author: John Hickey is a second year Biomedical Engineering PhD candidate in the Jon Schneck lab researching the use of different biomaterials for immunotherapies and microfluidics in identifying rare immune cells.
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