Spectrin coiled-coil

The leucine zipper DNA-binding proteins, described in Chapter 10, are examples of globular proteins that use coiled coils to form both homo- and heterodimers. A variety of fibrous proteins also have heptad repeats in their sequences and use coiled coils to form oligomers, mainly dimers and trimers. Among these are myosin, fibrinogen, actin cross-linking proteins such as spectrin and dystrophin as well as the intermediate filament proteins keratin, vimentin, desmin, and neurofilament proteins. 

Aetin binding domain Plakin domain Spectrin repeals xmxa Coiled coil rod domain Plakin repeals... 

Fig. 1. Structure of spectrin superfamily proteins. Modular domains within each protein are clearly defined. Shaded spectrin repeats represent coiled coils involved in dimerization events incomplete repeats represent proportionally the number of coiled-coil helices contributed by a- and /3-spectrin when generating a complete spectrin repeat during formation of the spectrin tetramer. The dashed lines indicate how two spectrin heterodimers interact to form a functional spectrin tetramer. Asterisks in the dystrophin spectrin repeats represent the position of the two greater repeats in dystrophin with respect to utrophin, which in all other respects has a similar overall structure. Numbers in the EF hand regions represent the number of EF hand motifs.

NCOCA- and NCACB-type experiments, such as those discussed in Section 2.6, were used to obtain an almost complete set of de novo resonance assignments for the SH3 domain of a-spectrin (62 residues, 7.2 kDa) under MAS conditions. " As discussed above, correlation of these ( N, C) chemical shift assignments with random coil values subsequently showed " that secondary chemical shifts provide a straightforward and powerful instrument with which to monitor secondary structure in solid-phase proteins under MAS conditions. Moreover, these resonance assignments represented the starting point for an investigation of the proton resonance frequencies and for the structural... 

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