Ultrafast rotation and trapping of carbon monoxide dissociated from myoglobin.
The nature of ligand motion within proteins has been investigated by measuring femtosecond time-resolved infrared (IR) spectra of CO photodissociated from the haem of myoglobin. Upon dissociation, the CO rotates approximately 90 degrees and becomes trapped within a ligand docking site located near the binding site. Two trajectories, distinguished spectroscopically and kinetically with time constants of 0.20 +/- 0.05 ps and 0.52 +/- 0.10 ps, lead to CO located within the docking site with opposite orientations. The protein reorganizes about the "docked' CO with a time constant of 1.6 +/- 0.3 ps and quickly establishes an energetic barrier that inhibits the reverse rebinding process.
Lim
M
M
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.
Jackson
T A
TA
Anfinrud
P A
PA
D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism*; D006736:Horses; D007700:Kinetics; D008024:Ligands; D008956:Models, Chemical; D009211:Myoglobin / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D012399:Rotation; D013055:Spectrophotometry, Infrared; D013997:Time Factors
D008024:Ligands; D009211:Myoglobin; C018013:carboxymyoglobin; D002245:Carbon Dioxide