Proteins also conformation

This idea also helps to explain some of the mystery surrounding the enormous catalytic power of enzymes In enzyme catalysis, precise orientation of catalytic residues comprising the active site is necessary for the reaction to occur substrate binding induces this precise orientation by the changes it causes in the protein s conformation. 

At ordinary pressure all the ionizable groups have their specific pK values and are present in ionized states according to these values. When pressure increases, we can expect all pK values to change, whereby the overall ionized state of the protein is changed. The whole hydration sheet may also be changed around the protein and conformational rearrangements may occur. This fact indicates that the volume of a protein may be very pressure-dependent. 

Formation of the bis-histidyl-heme complex also produces characteristic alterations in the protein s conformation, particularly in the environment of aromatic amino acids, notably tryptophan. Exposure of Trp residues to solvent decreases (113), Trp fluorescence is quenched (111), and an unusual band of positive ellipticity at 230 nm attributable to Trp is nearly doubled in intensity (Fig. 4) (104, 111, 124). 

Soluble proteins have a more complex structure than the fibrous, completely insoluble structural proteins. The shape of soluble proteins is more or less spherical (globular). In their biologically active form, globular proteins have a defined spatial structure (the native conformation). If this structure is destroyed (denaturation see p. 74), not only does the biological effect disappear, but the protein also usually precipitates in insoluble form. This happens, for example, when eggs are boiled the proteins dissolved in the egg white are denatured by the heat and produce the solid egg white. 

The physical environment within a crystal, of course, is not identical to that in solution or in a living cell. A crystal imposes a space and time average on the structure deduced from its analysis, and x-ray diffraction studies provide little information about molecular motion within the protein. The conformation of proteins in a crystal could in principle also be affected by nonphysiological factors such as incidental... 

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