CD FG F H G E AB GH EF
1.3.5 Increasing concentrations of H+(with a decrease of ph)or CO2 lowers the O2 affinity of hemoglobin(H+ and co, has no effect on o2 affinity of myoglobin). This is called Bohr effect, which helps the release of o, in the capillaries of actively metabolizing tissues (melecular mechanism?) 1.3.6 One molecule of 2, 3-diphosphoglycerate (BPG binds to the central cavity of one tetramer of hemoglobin, which lowers its O2 affinity. 1.3.7 Fetal hemoglobin (HbF)binds BPg less strongly than does hemoglobin a (adult) and consequently has a higher oxygen affinity(physiological function? Extraction of o2 from the mother)
1.3.5 Increasing concentrations of H+ (with a decrease of pH) or CO2 lowers the O2 affinity of hemoglobin (H+ and CO2 has no effect on O2 affinity of myoglobin). This is called Bohr effect, which helps the release of O2 in the capillaries of actively metabolizing tissues. (melecular mechanism?) 1.3.6 One molecule of 2,3-diphosphoglycerate (BPG) binds to the central cavity of one tetramer of hemoglobin, which lowers its O2 affinity. 1.3.7 Fetal hemoglobin (HbF) binds BPG less strongly than does hemoglobin A (adult) and consequently has a higher oxygen affinity. (physiological function? Extraction of O2 from the mother)
1. 4 Cooperativity is a particular case of an allosteric effect 1. 4.1 Allosteric effect refers to the phenomenon in which a molecule(allosteric effector) bound to one site on a protein causes a conformational change in the protein such that the activity of another site on the protein is altered (increased or decreased). 1.4.2 H+, Co2, and BPg all show an allosteric effect (heterotrophic? )for the O2 binding process of hemoglobin
1.4 Cooperativity is a particular case of an allosteric effect 1.4.1 Allosteric effect refers to the phenomenon in which a molecule (allosteric effector) bound to one site on a protein causes a conformational change in the protein such that the activity of another site on the protein is altered (increased or decreased). 1.4.2 H+, CO2 , and BPG all show an allosteric effect (heterotrophic?) for the O2 binding process of hemoglobin
1.5 Two models have been proposed to explain the allosteric regulation phenomena 1.5.1 The sequential model (proposed by Daniel Koshland, Jr) hypothesizes that the binding of one ligand to one subunit changes the conformation of that particular subunit from the T state(with a low activity) to the r state(with a high acitvity), a transition that increases the activity of the other subunits for the ligand 1.5.2 The sequential model can be analogized to the tearing process of postage stamps.(see fig
1.5 Two models have been proposed to explain the allosteric regulation phenomena 1.5.1 The sequential model (proposed by Daniel Koshland, Jr.) hypothesizes that the binding of one ligand to one subunit changes the conformation of that particular subunit from the T state (with a low activity) to the R state (with a high acitvity), a transition that increases the activity of the other subunits for the ligand. 1.5.2 The sequential model can be analogized to the tearing process of postage stamps. (see fig.)
1.5.3 The concerted model (proposed by monod Wyman, and Changeux) hypothesizes that symmetry in the same conformation) and the binding of each is conserved in allosteric transitions(all subunits ar ligand increases the probability that all subunits in that molecule are converted to the r-state(with a high activity). All-or-none model 1.5.4 The interplay between these different ligand-binding sites is mediated primarily by changes in quaternary structure. The contact region between two subunits can serve as a switch that transmits conformational changes from one subunit to another
1.5.3 The concerted model (proposed by Monod, Wyman, and Changeux) hypothesizes that symmetry is conserved in allosteric transitions (all subunits are in the same conformation) and the binding of each ligand increases the probability that all subunits in that molecule are converted to the R-state (with a high activity). All-or-none model. 1.5.4 The interplay between these different ligand-binding sites is mediated primarily by changes in quaternary structure. The contact region between two subunits can serve as a switch that transmits conformational changes from one subunit to another