Classes Conformational changes

Many stereoselective reactions have been most thoroughly studied with steroid examples because the rigidity of the steroid nucleus prevents conformational changes and because enormous experience with analytical procedures has been gathered with this particular class of natural products (J. Fried, 1972). The name steroids (stereos (gr.) = solid, rigid) has indeed been selected very well, if one considers stereochemical problems. We shall now briefly point to some other interesting, more steroid-specific reactions. 

From the crystal structure of the complex (Fig. 10) it appears that only minimal conformational changes occur within the MoFe protein on complexation, although it is hard to be dogmatic about these when at 3 A resolution. Nevertheless, ENDOR 116) studies on the FeMoco center demonstrated that at least one class of protons in the vicinity of the FeMoco center is altered in the complex relative to the free protein. 

In this chapter, it will be described how we have utilized endogenous and engineered Zn2+ binding sites to explore the structure and molecular function of Na+/Cl -depen-dent neurotransmitter transporters. The work has not only allowed the definition of the first structural constraints in the tertiary structure of this class of transporters, but also provided new insight into both conformational changes accompanying substrate translocation and mechanisms governing conformational isomerization in the translocation cycle. In the chapter, we will also review the theoretical and practical basis for... 

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