Backbone amide mutagenesis to understand the energetics of hydrogen-bonding in protein folding

ORGN 249

Jeffery W. Kelly, jkelly@scripps.edu1, Evan T Powers, epowers@scripps.edu1, Songpon Deechongkit1, Jan G Bieschke, jbiesch@scripps.edu2, Yanwen Fu, fuyan@scripps.edu1, Gianmin Gao1, and Philip E. Dawson3. (1) Department of Chemistry, The Scripps Research Institute, 10550 N. Torrey Pines Rd., La Jolla, CA 92037, (2) Department of Chemistry and The Skaggs Institute of Chemical Biology, Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, (3) Department of Cell Biology and Chemistry, The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 N. Torrey Pines Rd. CVN-6, La Jolla, CA 92037
Traditional mutagenesis reveals that the hydrophobic effect is a major driving force for protein folding. Much less is known about the contributions of hydrogen bonding (H-bonding) to protein structure acquisition because it has proven difficult to perturb amide bonds. We developed methods to replace amide bonds by E-olefin or ester bonds to perturb backbone H-bonds. We also measured the transfer free energies of equivalent amide, ester and E-olefin containing peptides or peptidomimetics, enabling correction of the perturbation free energy data to quantify H-bond energies. We provide evidence that only a subset of the H-bonds in a protein contribute significantly to the free energy of the native state, those enveloped by a hydrophobic core. Residues that make energetically important H-bonds often contribute a side-chain to the hydrophobic core. Data will be presented to support the hypothesis that H-bond strengths under these circumstances appear to be thermodynamically linked to the hydrophobic effect.
 

Peptide Bond Isosteres
8:10 AM-12:00 PM, Monday, 11 September 2006 Moscone Center -- Room 135, Oral

Division of Organic Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006