Nonexponential protein relaxation: dynamics of conformational change in myoglobin.
The picosecond evolution of the tertiary conformation of myoglobin (Mb) after photodissociation of MbCO was investigated at room temperature by probing band III, a weak iron-porphyrin charge-transfer transition near 13,110 cm-1 (763 nm) that is sensitive to the out-of-plane displacement of the iron. Upon photolysis, the iron moves out of the plane of the porphyrin, causing a blue-shift of band III and a concomitant change in the protein conformation. The dynamics for this functionally important motion are highly nonexponential, in agreement with recent molecular dynamics simulations [Kuczera, K., Lambry, J.-C., Martin, J.-L. & Karplus, M. (1993) Proc. Natl. Acad. Sci. USA 90, 5805-5807]. The conformational change likely affects the height of the barrier to ligand rebinding and may explain nonexponential NO rebinding.
Department of Chemistry, Harvard University, Cambridge, MA 02138.
M
M
Lim
T A
TA
Jackson
P A
PA
Anfinrud
D002942:Circular Dichroism; D007700:Kinetics; D007834:Lasers; D009211:Myoglobin / Q000737:chemistry*; D010782:Photolysis; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013997:Time Factors
D009211:Myoglobin; C018013:carboxymyoglobin