Troponin structure prediction

Figure 10-4. The structure of the calciumbinding protein troponin from chicken skeletal muscle. Although this is an exceptionally complicated ligand to a coordination chemist, the binding of calcium ions is to the hard donor sites that might be predicted. Binding of the calcium triggers a conformational change.

The actual picture of the troponin head, however, could not have been fully anticipated before the recent crystal structures of the Ca2+-activated cardiac (not shown) and skeletal troponin head region (Fig. 6C and D), both of which contain all three subunits (Takeda et al., 2003) (Vinogradova et al., 2005). To be sure, one can easily recognize the previously observed or predicted features such as the IT coiled-coil in these structures, as well as the contacts made between the TnC lobes and... 

Fig. 12. Predicted approximate quaternary structure of troponin-tropomyosin. Tj and Ta, Ti and Tj regions of troponin T C, troponin C TM, tropomyosin O, position of N terminus O, position of C terminus. Symbols (l), ( ), and (3) indicate four calcium...

The initial event in the contraction of skeletal muscles is generally assumed to be the binding of calcium ions to troponin C, one of three subunits in the protein complex, troponin, on the actin thin filament. Troponin C (MW 18,000) contains 46 carboxylic groups out of a total of 159 amino acids (26). Based on primary structure analogies between parvalbumin, the crystal structure of which is known, and troponin C (TnC), Kretsinger and Barry have predicted the location and general structure of four... 

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