NH2-terminal truncation of skeletal muscle troponin T does not alter the Ca2+ sensitivity of thin filament assembly

44Citations
Citations of this article
10Readers
Mendeley users who have this article in their library.

This article is free to access.

Abstract

To investigate how Ca2+ binding to troponin C regulates muscle contraction, the Ca2+-sensitive properties of thin filament assembly were studied as the tropomyosin binding, NH2-terminal region of troponin T was progressively shortened. Troponin complexes were prepared that contained skeletal muscle troponin C, troponin I, and either intact troponin T (TnT) (residues 1-259) or fragment TnT-(70-259), TnT-(151-259), or TnT-(159-259). In the absence of Ca2+ their respective affinities for pyrene-labeled tropomyosin were 2.3 × 107 M-1, 1.2 × 107 M-1, 1.9 × 105 M-1, and 1.9 × 105 M-1. Ca2+ had only a small effect on these affinities: 1.1 × 107 M-1 for whole troponin, 2 × 105 M-1 for troponin-(151-259), and 2.8 × 105 M-1 for troponin-(159-259). Forms of troponin that bound weakly to tropomyosin in the absence of actin increased the actin affinity of tropomyosin only 2-3-fold, even in the absence of Ca2+; weak binding of troponin to tropomyosin correlated with weak effects on tropomyosin-actin binding. In contrast, whole troponin had an approximately 500-fold effect on tropomyosin binding to actin, regardless of whether Ca2+ was present. The small effect of Ca2+ on the energetics of thin filament assembly is not attributable to the amino-terminal region of troponin T. The results suggest that Ca2+ causes the interaction between actin and the globular region of troponin to switch between two energetically similar states.

Cite

CITATION STYLE

APA

Fisher, D., Wang, G., & Tobacman, L. S. (1995). NH2-terminal truncation of skeletal muscle troponin T does not alter the Ca2+ sensitivity of thin filament assembly. Journal of Biological Chemistry, 270(43), 25455–25460. https://doi.org/10.1074/jbc.270.43.25455

Register to see more suggestions

Mendeley helps you to discover research relevant for your work.

Already have an account?

Save time finding and organizing research with Mendeley

Sign up for free