Proline-Rich Sequences and Polyproline II Helix Formation

The aim of this project is to determine how proline-rich left-handed polyproline II (PPII) helices form. PPII helices are common in proteins and often play vital roles in critical processes including signal transduction, cell motility, transcription and immune response. PPII helices are involved in both structural roles (e.g., as adopted by collagen) and molecular recognition (e.g., protein-protein interactions mediated by SH3 domains). It is commonly assumed that many proline-rich regions of sequence (PRR's) adopt this confirmation. The goal of this project is to determine the physical basis for PPII helices. This will be achieved via systematic host-guest experiments using a poly(proline)-based host peptide known to form a PPII helix. A combination of experimental and computational methods will be employed. Circular dichroism will be used to measure average PPII helical content of host-guest peptides in order to determine contributions of both individual residues and pairs of residues to the formation of PPII helices. High resolution nuclear magnetic resonance spectroscopy, and molecular dynamics computer simulations will be used to examine the atomic-level interactions that lead to the favoring or disfavoring PPII helix formation. The data obtained from all of these experiments will be combined to form a comprehensive atomic-level picture of PPII helix formation by PRR's. The results of this project will be applicable to studies of a multitude of critical physiological processes ranging from signal transduction to transcription to cell motility. This project lays essential groundwork for future studies of protein-protein interactions involving PPII helices formed by PRR's.