Structural determinants of ligand binding to ATP dependent enzymes: Studies of Protein Kinase and Heat Shock Protein 70.

Abstract

Enzymes are protein molecules that accelerate, or “catalyze”, specific chemical reactions. The reacting molecules, or substrates, bind to the enzyme which then enables their effective conversion into different product molecules. Virtually all metabolic processes in the cell need enzymes to occur at speeds fast enough to maintain life. The kinases are a large group of phosphotransferases, i.e. enzymes which catalyze the transfer of the gamma-phosphate group from an adenosine-5-triphosphate (ATP, as phosphate donor) to a hydroxyl group (acceptor) of specific substrates. Protein kinases transfer the phosphate groups to other proteins as substrates. These processes enable the cell to transfer signals between different components of the cell that control essential processes. Tyrosine protein kinases transfer them to the phenolic hydroxyl group of amino acid residues in proteins called tyrosine, while serine/threonine protein kinases transfer the phosphate groups to the alcohol group of the serine or threonine amino acid residues. Protein kinases also represent a key interest in the pharmaceutical industry, because they are considered therapeutic targets for diseases, including e.g. diabetes, neurodegenerative diseases, Alzheimer's disease, herpes simplex virus infection, malaria, but especially for cancer. Since the year 2001, some 30 cancer drugs that block the activity of cancer causing protein kinases have been approved.

This project describes basic chemical research of protein-ligand interactions, using key cancer drug targets as model enzymes. The research is designed to advance basic knowledge of the chemical recognition mechanisms of enzymes, and enable the design of new and improved therapeutic inhibitors. The first part of this work, represented by two published papers and a submitted manuscript, analyzes inhibitor interactions in key tyrosine protein kinases involved in cancers, including Abl (a leukemia target) and EGFR (a lung cancer target). These analyses optimize approaches to identify new inhibitors with potentially improved protein kinase inhibition profiles to forestall the development of drug resistance. The second part analyses the ATP and potential inhibitor binding site of a different class of enzyme involved in cancer, a “heat shock protein”. Finally, a draft manuscript analyses the geometric variability of a key amino acid residue of protein kinases that is often involved in drug resistance generation. The key technologies used in this project are chemical synthesis; enzyme purification, crystallography, SPR spectroscopy, and molecular modeling.