Secondary active transporters binding protein dependent

This tertiary structure of a protein is extraordinarily important because it determines the shape of these huge molecules and biological activity depends intimately on these shapes. Evolution has produced proteins that have pockets into which specific molecules called substrates fit. This enzyme-substrate binding allows for the proper orientation for reaction of the substrate. The reaction could be complicated, or as simple as the hydrolysis of an ester. In other molecules, substrates are bound only for transportation purposes. These binding sites are a direct consequence of the primary structure that determines the secondary and tertiary structures. Figure 23.25 gives a schematic representation of this process. 

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