Oxygen equilibrium properties of myoglobin locked in the liganded and unliganded conformations.
A comparison of the O(2) equilibrium curves of sperm-whale myoglobin locked in the liganded (CO-bound) and unliganded (deoxy) conformations by encapsulation in a wet porous sol-gel silica reveals a marked difference between them. The CO-bound state-locked myoglobin showed a nearly monophasic (hyperbolic) O(2) equilibrium curve with a dissociation constant of 0.2 Torr, which is smaller than that of myoglobin in solution (0.5 Torr). On the other hand, the deoxy state-locked myoglobin exhibited a multiphasic O(2) equilibrium curve that can be represented by a sum of three independent components with dissociation constants of 0.19, 0.90, and 44 Torr, respectively, indicating that deoxymyoglobin exists in multiple conformations. These results show that myoglobin can be frozen into ligand-dependent conformational populations at room temperature in the wet sol-gel and suggest that the overall O(2) equilibrium properties of myoglobin in solution are generated by a redistribution of protein conformational populations in response to ligand binding.
Shibayama
Naoya
N
Department of Physiology, Division of Biophysics, Jichi Medical School, Yakushiji 3311-1, Minamikawachi, Kawachi, Tochigi 329-0498, Japan. shibayam@jichi.ac.jp
Saigo
Satoshi
S
D000818:Animals; D002248:Carbon Monoxide / Q000737:chemistry* / Q000378:metabolism; D005782:Gels; D007700:Kinetics; D008024:Ligands; D009211:Myoglobin / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D014907:Whales
D005782:Gels; D008024:Ligands; D009211:Myoglobin; C055547:deoxymyoglobin; D002248:Carbon Monoxide; D010100:Oxygen