Central helix role in the contraction‐relaxation switching mechanisms of permeabilized skeletal and smooth muscles with genetic manipulation of calmodulin

FEBS Letters

Babu, Árvind¹  Persechini, Anthony¹  Gulati, Jagdish¹ 

[1] Albert Einstein College of Medicine, Departments of Medicine and Physiology/Biophysics, Division of Cardiology, 1300 Morris Park Avenue, Bronx, NY 10461 USA

关键词: Calcium;    Troponin C;    Parvalbumin;    Oncomodulin;    CaM;    calmodulin;    TnC;    troponin-C;    TnI;    troponin I;    TnT;    troponin T;    TM;    tropomyosin;    LCs;    myosin light chains;    EDTA;    ethylene diamine tetraacetic acid;    EGTA;    ethylene glycol bis(β-aminoethyl ether)-N;    N′-tetraacetic acid;    SDS-PAGE;    sodium dodecyl sulfate polyacrylamide gel electrophoresis;   

DOI  :  10.1016/0014-5793(90)81409-H

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

A prominent common feature of calmodulin and troponin structures is the unusually long central helix which separates the two lobes, each containing two Ca²⁺-binding sites. To study the role of certain highly conserved residues in the helix in the contraction-relaxation switching mechanism in muscle, we measured the Ca²⁺-activated force of permeabilized skeletal and smooth muscles with three genetically manipulated forms of calmodulin. Mutated calmodulin was made to substitute for troponin-C in vertebrate skeletal fiber. The mutants had 1–4 deletions in the conserved cluster (positions 81–84) in the solvent-exposed region of the central helix, which also substantially shortened the helix. The force of the maximally activated fiber was found to be diminished only with the mutant in which the entire cluster Ser-81 to Glu-84 (CaMΔ81–84) was deleted. All such deletions were found to be completely ineffective in blocking the Ca²⁺-switching process in smooth muscle strips. The results show for the first time that at least a part of the highly conserved four-residue cluster in the central helix is critical for the contraction mechanism of striated muscle. Further, the possibility is raised that the reduced length of the central helix may be a determining factor in the Ca²⁺-switching mechanism in fast-twitch muscle. These findings combined with the results on smooth muscle indicate diversity in the structure-function specifications for the central helix of calmodulin for different target proteins.

【 授权许可】

Unknown