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The three‐dimensional structure of troponin‐C: Supersecondary structural homology of calcium binding folds
Author(s) -
Sundaralingam M.,
Rao S. T.,
Drendel W.,
Greaser M. L.
Publication year - 2009
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560280715
Subject(s) - troponin c , crystallography , chemistry , calcium , calcium binding protein , parvalbumin , helix (gastropod) , biophysics , binding site , troponin , biology , biochemistry , genetics , psychology , ecology , organic chemistry , psychiatry , myocardial infarction , snail
The X‐ray structure of chicken troponin‐C at 3 Å resolution was recently reported [1]. The structure exhibits an unusual dumbbell shape with the–COOH and—NH 2 domains connected by a long α‐helix of about nine turns. Only the two Ca 2+ ‐binding sites of the—COOH domain are occupied by metal ions. The individual helix‐loop‐helix (HLH) calcium‐binding motifs as well as the combined calcium‐binding sites in the—COOH domain exhibit a supersecondary structure similar to that of parvalbumin. However, the helix–loop–helix supersecondary structure of the two putative calcium‐binding folds (metal free) in the—NH 2 domain, while similar to each other, are markedly different from those of the—COOH domain. The conformational differences between the four Ca 2+ (wherein the HLH regions of the—NH 2 domain also display the same conformation as the—COOH domain) and two Ca 2+ states of TnC would provide a better insight into the conformational changes in TnC and the molecular interactions of TnC with TnI and TnT in the troponin complex.