Biochemistry Online: An Approach Based on Chemical Logic

Biochemistry Online

CHAPTER 5 - BINDING

C:  MODEL BINDING SYSTEMS

BIOCHEMISTRY - DR. JAKUBOWSKI

3/29/16

Learning Goals/Objectives for Chapter 5C:  After class and this reading, students will be able to

  • explain the similarities and differences in structure between myoglobin and hemoglobin in the deoxy and oxy states
  • state structural features of Hb that stabilizes the deoxystate and the oxystate
  • draw graphs of fractional saturation Y vs L (or pO2) for Mb and Hb  (at different pHs and in the presence of CO2 for Hb) and explain their apparent similarities and differences
  • draw a thermodynamic cycle for the interactions of O2, CO2 and H+ with deoxy-Hb and oxy-Hb
  • explain how Hill Plot analysis can account for cooperative binding curves for Hb.
  • give a simple explanation of the MWC model and draw cartoon representations of Hb in the T and R state, describing the characteristics of those states
  • given definitions of the MWC parameters (L, KT, KR, c, and α) and the assumptions of the model, explain how this model accounts for cooperative sigmoidal binding curves for Hb and dioxygen.
  • draw cartoon models and explain differences in lock and key, induced fit, and conformational selection as mechanisms for ligand bind.
  • Explain biological advantages elicited on ligand binding by intrinsically disordered proteins

C5.  Mathematical Analysis of Cooperative Binding - KNF Sequential Model

 This KNF (Koshland, Nemethy, and Filmer) Sequential Model:model was developed to address concerns with the concerted model. One of the major problems with the concerted model is that it seemed unrealistic to expect all the subunits to change conformation together. Why shouldn't there be some difference in subunit conformation? The KNF model also fits the experimental data well. 

Figure:  EQUILIBRIA IN KNF MODEL

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