Applications of linear and cyclic peptides as enzyme inhibitors and molecular transporters

Guofeng Ye, University of Rhode Island

Abstract

The diversity of amino acids in peptides allows the design of different linear or cyclized compounds. Peptides can be designed to act as inhibitors, probes, or molecular transporters of other molecules. The objective of this dissertation research was to exploit the diversity of peptide structures and focused on developing linear and cyclic peptides as c-Src inhibitors and using the information derived from c-Src crystal structure to design novel peptide-based molecular transporters.^ A series of peptide analogues of Ac-CIYKYY were designed and synthesized to improve the inhibitory potency against active Src Linear peptide Ac-CIYKF(4-NO 2)Y (IC50 = 0.53 μM) and a conformationally constrained peptide derived from cyclization between Y3 and K4 (IC 50 = 0.28 μM) exhibited 750- and 1400-fold higher inhibitory activities, respectively, versus Ac-CIYKYY (IC50 = 400 μM). In another approach to design Src SH2 domain binding ligand, four pYEEI peptide derivatives containing 0-2 metal chelating iminodiacetate (IDA) groups at the N- and C-terminal lysine residues, such as Ac-K(IDA)pYEEIEK(IDA), were synthesized and evaluated. Peptides containing IDA groups can be valuable tools for studying protein-substrate interactions.^ Based on the three key positively charged residues (Arg, Arg, and Lys) surrounding the phosphotyrosine binding pocket of Src SH2 domain, we designed three classes of branched tripodal peptides as molecular transporters for phosphopeptides. Fluorescence microimaging cellular uptake studies with fluorescein-attached linear peptide analogue 4 (FLPA4) alone or with the mixture of LPA4 and F-GpYEEI in BT-20 cells showed dramatic increase of the fluorescence intensity in cytosol of the cells, indicating that LPA4 can function as a delivery tool of F-GpYEEI across the cell membrane. The mechanism of differential interactions of such compounds with different lipid membrane systems was investigated by differential scanning calorimetry and fluorescence spectroscopy. The peptides were found to bind to the negatively-charged headgroups, significantly affecting melting behavior and inducing domain formation.^ These studies indicated the potential applications of artificial peptides for inhibitor design and molecular transporters. ^

Subject Area

Chemistry, Pharmaceutical|Health Sciences, Pharmacy

Recommended Citation

Guofeng Ye, "Applications of linear and cyclic peptides as enzyme inhibitors and molecular transporters" (2008). Dissertations and Master's Theses (Campus Access). Paper AAI3346862.
http://digitalcommons.uri.edu/dissertations/AAI3346862

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