PMID: 7552748

Authors:

Kuboniwa H, Tjandra N, Grzesiek S, Ren H, Klee CB, Bax A

Title:

Solution structure of calcium-free calmodulin.

Journal:

Nat Struct Biol. 1995 Sep;2(9):768-76.

Abstract:

The three-dimensional structure of calmodulin in the absence of Ca2+ has been determined by three- and four-dimensional heteronuclear NMR experiments, including ROE, isotope-filtering combined with reverse labelling, and measurement of more than 700 three-bond J-couplings. In analogy with the Ca(2+)-ligated state of this protein, it consists of two small globular domains separated by a flexible linker, with no stable, direct contacts between the two domains. In the absence of Ca2+, the four helices in each of the two globular domains form a highly twisted bundle, capped by a short anti-parallel beta-sheet. This arrangement is qualitatively similar to that observed in the crystal structure of the Ca(2+)-free N-terminal domain of troponin C.