The conformation of calmodulin: A substantial environmentally sensitive helical transition in Ca4‐calmodulin with potential mechanistic function

FEBS Letters

Martin, Stephen¹  Jones, Gareth²  Bayley, Peter¹ 

[1] Division of Physical Biochemistry, National Institute for Medical Research, Mill Hill, London NW7 1AA, England;MRC-SERC Biology Support Laboratory, Daresbury Laboratory, Warrington WA4 4AD, England

关键词: Calmodulin;    Helical content;    Circular dichroism;    Conformation;    Fluorescence anisotropy;    Rotational correlation;    TNS;    2-p-toluidinylnaphthalene-6-sulfonic acid;    Mes;    2-(N-morpholino)ethanesulfonic acid;    TFE;    2;    2;    2-trifluoroethanol;   

DOI  :  10.1016/0014-5793(88)80225-4

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The conformation of Ca₄-calmodulin in solution, as assessed by far-UV peptide circular dichroism, contains significantly less α-helix than the proposed X-ray crystal structure. We now show that Ca₄-calmodulin adopts significant additional helical structure in solution in the presence of a helicogenic solvent (50%, v/v, aqueous 2,2,2-trifluoroethanol or 50%, v/v, methylpentane-5,5-diol). We suggest that the long continuous helix (residues 66–92 of the crystal structure)is not necessarily a normal feature of the calmodulin structure in solution, and may be due in part to the conditions of crystallisation. This result is supported by time-resolved tyrosine fluorescence anisotropy studies indicating that Ca₄-calmodulin in solution is an essentially compact globular structure which undergoes isotropic rotational motion. We conclude that, under appropriate ionic and apolar environmental conditions, Ca₄-calmodulin undergoes a substantial helical transition, which may involve residues in the central region of the molecule. Such a transition could have an important function in determining specificity and affinity in interactions of calmodulin with different target sequences of Ca²⁺-dependent regulatory enzymes.

【 授权许可】

Unknown