The role of the NH2- and COOH-terminal domains of the inhibitory region of troponin I in the regulation of skeletal muscle contraction

Danuta Szczesna, Ren Zhang, Jiaju Zhao, Michelle Jones, James D. Potter

Research output: Contribution to journalArticle

14 Scopus citations

Abstract

The role of the inhibitory region of troponin (Tn) I in the regulation of skeletal muscle contraction was studied with three deletion mutants of its inhibitory region: 1) complete (TnI-(Δ96-116)), 2) the COOH-terminal domain (TnI-(Δ105-115)), and 3) the NH2-terminal domain (TnI-(Δ95-106)). Measurements of Ca2+-regulated force and relaxation were performed in skinned skeletal muscle fibers whose endogenous TnI (along with TnT and TnC) was displaced with high concentrations of added troponin T. Reconstitution of the Tn-displaced fibers with a TnI·TnC complex restored the Ca2+ sensitivity of force; however, the levels of relaxation and force development varied. Relaxation of the fibers (pCa 8) was drastically impaired with two of the inhibitory region deletion mutants, TnI-(Δ96-116)·TnC and TnI-(Δ105- 115)·TnC. The TnI-(Δ95-106)·TnC mutant retained ~55% relaxation when reconstituted in the Tn-displaced fibers. Activation in skinned skeletal muscle fibers was enhanced with all TnI mutants compared with wild-type TnI. Interestingly, all three mutants of TnI increased the Ca2+ sensitivity of contraction. None of the TnI deletion mutants, when reconstituted into Tn, could inhibit actin-tropomyosin-activated myosin ATPase in the absence of Ca2+, and two of them (TnI-(Δ96-116) and TnI(Δ105-115)) gave significant activation in the absence of Ca2+. These results suggest that the COOH terminus of the inhibitory region of TnI (residues 105-115) is much more critical for the biological activity of TnI than the NH2-terminal region, consisting of residues 95-106. Presumably, the COOH-terminal domain of the inhibitory region of TnI is a part of the Ca2+-sensitive molecular switch during muscle contraction.

Original languageEnglish (US)
Pages (from-to)29536-29542
Number of pages7
JournalJournal of Biological Chemistry
Volume274
Issue number41
DOIs
StatePublished - Oct 8 1999

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Fingerprint Dive into the research topics of 'The role of the NH<sub>2</sub>- and COOH-terminal domains of the inhibitory region of troponin I in the regulation of skeletal muscle contraction'. Together they form a unique fingerprint.

  • Cite this