The crystal structure of the C-terminal fragment of striated-muscle -tropomyosin reveals a key troponin T recognition site

摘要

Contraction in striated and cardiac muscles is regulated by the motions of a Ca~2+ -sensitive tropomyosin/troponin switch. In con- trast, troponin is absent in other muscle types and in nonmuscle cells, and actomyosin regulation is myosin-linked. Here we report an unusual crystal structure at 2.7 A of the C-terminal 31 residues of rat striated-muscle -tropomyosin (preceded by a fragment of the GCN4 leucine zipper). The C-terminal 22 residues (263-284) of the structure do not form a two-stranded -helical coiled coil as does the rest of the molecule, but here the -helices splay apart and are stabilized by the formation of a tail-to-tail dimer with a symmetry-related molecule.