Probing the role of hydration in the unfolding transitions of carbonmonoxy myoglobin and apomyoglobin.
We show that the equilibrium unfolding transition of horse carbonmonoxy myoglobin monitored by the stretching vibration of the CO ligand, a local environmental probe, is very sharp and, thus, quite different from those measured by global conformational reporters. In addition, the denatured protein exhibits an A(0)-like CO band. We hypothesize that this sharp transition reports penetration of water into the heme pocket of the protein. Parallel experiments on horse apomyoglobin, wherein an environment-sensitive fluorescent probe, nile red, was used, also reveals a similar putative hydration event. Given the importance of dehydration in protein folding and also the recent debate over the interpretation of probe-dependent unfolding transitions, these results have strong implications on the mechanism of protein folding.
Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Lin
L
Guo
Jaeheung
J
Park
Taegon
T
Lee
Pramit
P
Chowdhury
Manho
M
Lim
Feng
F
Gai
D000818:Animals; D001059:Apoproteins / Q000737:chemistry*; D002248:Carbon Monoxide / Q000737:chemistry*; D006736:Horses; D008024:Ligands; D009211:Myoglobin / Q000737:chemistry*; D017510:Protein Folding; D013997:Time Factors; D014732:Vibration; D014867:Water / Q000737:chemistry*
D001059:Apoproteins; D008024:Ligands; D009211:Myoglobin; C010857:apomyoglobin; C018013:carboxymyoglobin; D014867:Water; D002248:Carbon Monoxide