Protein ligand migration mapped by nonequilibrium 2D-IR exchange spectroscopy.
2D-IR exchange spectroscopy has been introduced recently to map chemical exchange networks in equilibrium with subpicosecond time resolution. Here, we demonstrate the generalization of 2D-IR exchange spectroscopy to nonequilibrium systems and its application to map light-triggered migration of ligands between different sites in a protein. Within picoseconds after a photodissociating laser pulse, carbon monoxide ligands relocate from their binding site A at the heme prosthetic group of myoglobin to a primary docking site B in the distal heme pocket. Multiple CO stretching bands are observed for the CO ligand in sites A and B, indicating that several distinct conformational substates of the myoglobin:ligand complex coexist in solution. Exchange cross-peaks between the bands associated with substates of heme-bound CO and photodissociated CO in the primary docking site reveal the substate connectivity at physiological temperature.
Bredenbeck
Jens
J
Physikalisch-Chemisches Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland. j.bredenbeck@pci.unizh.ch
Helbing
Jan
J
Nienhaus
Karin
K
Nienhaus
G Ulrich
GU
Hamm
Peter
P
D000818:Animals; D008024:Ligands; D009154:Mutation / Q000235:genetics; D009211:Myoglobin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013055:Spectrophotometry, Infrared / Q000379:methods*; D013552:Swine; D014633:Valine / Q000235:genetics / Q000378:metabolism
D008024:Ligands; D009211:Myoglobin; D014633:Valine