Søren Wittrup Pedersen

September 2002 - July 2007:
M.Sc. (Pharm), Faculty of Pharmaceutical Sciences, University of Copenhagen

September 2008 - April 2009:
Research Assistant, ChemBiol, Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen

May 2009:
Ph.D Student, ChemBiol, Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen

Semisynthesis of glutamate receptors and associated proteins by expressed protein ligation

Background:
The ionotropic glutamate (iGlu) receptors are a part of a complex signalling network within the brain. The function of these receptors is essential for basic neurotransmission and any disturbances in this tightly regulated system can have devastating consequences [1]. Thus it is of great interest to gain information about the structure and function of the iGlu receptors and interacting proteins so possible harmful neurodegenerative processes can be prevented [2].

The objective of this project is use a semi-synthetic approach to design and generate protein constructs mimicking the iGlu receptors and associated proteins. The goal is to incorporate unnatural occurring amino acids into iGlu related proteins and thereby explore the structural importance of specific amino acid residues.

These new proteins can be engineered by a technique called expressed protein ligation (EPL), which combines advantages of chemical peptide synthesis with molecular biology. The modified proteins will be prepared from two fragments;

• a peptide synthesized by solid-phase peptide synthesis (SPPS), which can be chemically modified to a great extent
• a recombinant produced protein obtained from bacterial expression, which allows larger proteins to be generated

These fragments can afterwards be fused together by EPL that relies on the reaction between an α-thioester peptide and a peptide with an N-terminal cysteine leading to a native peptide bond [3, 4].

It is intended that the final protein will be used for structure-activity relationship studies as well as X-ray studies.

1. Dingledine, R., et al., The glutamate receptor ion channels. Pharmacol Rev, 1999. 51(1): p. 7-61.
2. Aarts, M., et al., Treatment of ischemic brain damage by perturbing NMDA receptor- PSD-95 protein interactions. Science, 2002. 298(5594): p. 846-50.
3. Dawson, P.E., et al., Synthesis of proteins by native chemical ligation. Science, 1994. 266(5186): p. 776-9.
4. Muir, T.W., D. Sondhi, and P.A. Cole, Expressed protein ligation: a general method for protein engineering. Proc Natl Acad Sci U S A, 1998. 95(12): p. 6705-10.

Bach, A.; Chi, C. N.; Olsen, T. B.; Pedersen, S. W.; Røder, M. U.; Pang, G. F.; Clausen, R. P.; Jemth, P.; Strømgaard, K. Modified peptides as potent inhibitors of the postsynaptic density-95/N-methyl-d-aspartate receptor interaction. J. Med. Chem. 2008, 51, 6450-6459.