Chapter 8 - Conformational States in Crystal and Nuclear Magnetic Resonance Structures

Abstract

This chapter reveals that conformational differences in crystal and Nuclear Magnetic Resonance (NMR) structures are difficult to determine. It highlights that data must be acquired and analyzed under conditions for both conformational states. To obtain information about conformational changes, atomic coordinates for the two states must be carefully compared for which; the coordinates should be close to superimposed. Two ways to establish conformational changes through the use of protein crystallography are described: (1) visual, and (2) mathematical. Both methods can also be used to study homologous proteins. The chapter states the example of the cooperative binding of oxygen to hemoglobin and makes a comparison of the two conformational states. The oxygenation of hemoglobin where two crystal conformations occur is also discussed. Conformational states in other crystallographic are then analyzed. The most studied example is the cooperative binding of oxygen to hemoglobin. The molecular structures of the oxy and deoxy forms (abbreviated HbO and deoxy-Hb, respectively) from several species have been studied. The transition from HbO to deoxy-Hb is a very complicated change in state. By studying the two conformations of Hb, it is possible to describe the most probable linkage of conformational changes that tie the binding of a small ligand to surface atoms to a subsequent rearrangement of subunits.