Book of Abstracts: Albany 2003
June 17-21 2003
Probing Molecular Recognition by Protein Kinases with Novel Peptide Mimics
Although a great deal of information is available on the recognition sequences of protein kinases, little is know about the binding conformation in which these sequences bind in the enzyme active site. Here we propose a novel hypothesis that at least some protein kinases recognize and phosphorylate their recognition sequences when these are in the poly-L-proline type II (PPII) conformation. We have devised a strategy for the construction of PPII mimics through the synthesis of peptides from what we call proline templated amino acids (PTAAs). PTAAs are specifically designed so that oligoPTAAs preferentially populate the PPII conformation in solution. This design strategy has been validated through solution studies of oligoPTAAs that show that indeed, oligoPTAAs do populate the PPII conformation in solution. In the first application of the PTAA methodology, we have explored the conformation in which peptides bind to the cGMP dependent protein kinase (PKG) active site. Our results with pseudo-substrate inhibitors provide strong evidence that substrates bind to the PKG active site in the PPII conformation. If our studies on the binding conformation of protein kinases show that additional protein kinases bind peptides in the PPII conformation this could have evolutionary, mechanistic and functional implications. Furthermore, PPII mimics could provide the basis for the design of selective protein kinase inhibitors. Towards the ends of designing selective inhibitors, we have begun developing methods for the facile synthesis of PPII mimic libraries. We will present our efforts towards this goal through the use of diversifiable PTAAs; i.e. PTAAs that can be diversified through a specific reaction after incorporation into a solid-supported, growing peptide chain. Although the diversification reaction may take many forms, we will focus on the diversification of proline-templated ornithines through guanidinylation and amidinylation reactions with a diversity of reagents.
1Department of Chemistry