Finding new tasks for the disruptive proteins in bee venom

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.

Figure 1: Membrane Active Peptide Schematic (Source: http://ins.sjtu.edu.cn/people/jakob/)

Figure 1: Membrane Active Peptide Schematic (Source: http://ins.sjtu.edu.cn/people/jakob/)

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.

For all press inquiries regarding INBT, its faculty and programs, contact Mary Spiro, mspiro@jhu.edu or 410-516-4802.

Making therapeutic proteins last longer

Happy TRAILs to you: PEGylation of proteins through complementary interactions between a His-tag and a Ni2+ complex of nitrilotriacetic acid (NTA, see picture), a well-established practice in protein research, was used to improve the half-life of therapeutic proteins in the blood following systemic administration in vivo. Animal models show that this site-specific modification improves the efficacy of modified TRAIL proteins.

Happy TRAILs to you: PEGylation of proteins through complementary interactions between a His-tag and a Ni2+ complex of nitrilotriacetic acid (NTA, see picture), a well-established practice in protein research, was used to improve the half-life of therapeutic proteins in the blood following systemic administration in vivo. Animal models show that this site-specific modification improves the efficacy of modified TRAIL proteins.

Proteins are responsible for pretty much everything in the human body. When there is a problem with the proteins, it usually leads to disease.

Protein therapy shows enormous potential for treating disease. But sometimes the proteins in a therapeutic treatment break down or are metabolized before they ever reach their target destination.

In a recent paper published in Angewandte Chemie, researchers from the laboratories of Martin Pomper (radiology oncology) and Seulki Lee (radiology, Center for Nanomedicine) at the Johns Hopkins School of Medicine and developed a simple method to validate protein drugs in animal models, said Lee. An illustration related to the paper appeared on the cover of the journal.

“We show that we can extend the half-life, that is, the amount of time the drug stays in the blood, while maintaining the activity of the model protein drug, TRAIL,” said one of the lead authors Maggie Swierczewska. “This has great implications for drug screening and validation methods, especially for the growing protein drug market.”

According to the paper, by attaching a molecule of  polyethylene glycol (PEG) to certain sites on the TRAIL protein drugs through an already well known method, the half-life of the drug could be extended without affecting its beneficial activity.

Authors on this paper include Tae Hyung Kim, Magdalena Swierczewska, Yumin Oh, AeRyon Kim, Dong Gyu Jo, Jae Hyung Park,  Youngro Byun, Scheherazade Sadegh-Nasseri, Martin G. Pomper, Kang Choon Lee, Seulki Lee. Author affiliations include the departments of Radiology and Pathology at the Johns Hopkins School of Medicine, the Johns Hopkins Center of Cancer Nanotechnology Excellence, the Johns Hopkins Institute for NanoBioTechnology, Center for Nanomedicine and collaborators at Sungkyunkwan University and Seoul National University, both in Korea.

Reference: Kim, T. H., Swierczewska, M., Oh, Y., Kim, A., Jo, D. G., Park, J. H., Byun, Y., Sadegh-Nasseri, S., Pomper, M. G., Lee, K. C. and Lee, S. (2013), Mix to Validate: A Facile, Reversible PEGylation for Fast Screening of Potential Therapeutic Proteins In Vivo. Angew. Chem. Int. Ed.. Vol. 52, Issue 27, pages 6880-6884, doi: 10.1002/anie.201302181