skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Calcium-dependent movement of troponin I between troponin C and actin as revealed by spin-labeling EPR

Abstract

We measured EPR spectra from a spin label on the Cys133 residue of troponin I (TnI) to identify Ca{sup 2+}-induced structural states, based on sensitivity of spin-label mobility to flexibility and tertiary contact of a polypeptide. Spectrum from Tn complexes in the -Ca{sup 2+} state showed that Cys133 was located at a flexible polypeptide segment (rotational correlation time {tau} = 1.9 ns) that was free from TnC. Spectra of both Tn complexes alone and those reconstituted into the thin filaments in the +Ca{sup 2+} state showed that Cys133 existed on a stable segment ({tau} = 4.8 ns) held by TnC. Spectra of reconstituted thin filaments (-Ca{sup 2+} state) revealed that slow mobility ({tau} = 45 ns) was due to tertiary contact of Cys133 with actin, because the same slow mobility was found for TnI-actin and TnI-tropomyosin-actin filaments lacking TnC, T or tropomyosin. We propose that the Cys133 region dissociates from TnC and attaches to the actin surface on the thin filaments, causing muscle relaxation at low Ca{sup 2+} concentrations.

Authors:
 [1];  [1];  [1];  [2]
  1. Department of Biological Sciences, Graduate School of Science, Osaka University and CREST/JST, Toyonaka, Osaka 560-0043 (Japan)
  2. Department of Biological Sciences, Graduate School of Science, Osaka University and CREST/JST, Toyonaka, Osaka 560-0043 (Japan). E-mail: arata@bio.sci.osaka-u.ac.jp
Publication Date:
OSTI Identifier:
20798791
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biochemical and Biophysical Research Communications; Journal Volume: 340; Journal Issue: 2; Other Information: DOI: 10.1016/j.bbrc.2005.12.030; PII: S0006-291X(05)02746-4; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; ACTIN; CALCIUM; CALCIUM IONS; ELECTRON SPIN RESONANCE; FILAMENTS; LABELLING; MUSCLES; POLYPEPTIDES; RELAXATION; SENSITIVITY; TROPOMYOSIN

Citation Formats

Aihara, Tomoki, Ueki, Shoji, Nakamura, Motoyoshi, and Arata, Toshiaki. Calcium-dependent movement of troponin I between troponin C and actin as revealed by spin-labeling EPR. United States: N. p., 2006. Web. doi:10.1016/j.bbrc.2005.12.030.
Aihara, Tomoki, Ueki, Shoji, Nakamura, Motoyoshi, & Arata, Toshiaki. Calcium-dependent movement of troponin I between troponin C and actin as revealed by spin-labeling EPR. United States. doi:10.1016/j.bbrc.2005.12.030.
Aihara, Tomoki, Ueki, Shoji, Nakamura, Motoyoshi, and Arata, Toshiaki. Fri . "Calcium-dependent movement of troponin I between troponin C and actin as revealed by spin-labeling EPR". United States. doi:10.1016/j.bbrc.2005.12.030.
@article{osti_20798791,
title = {Calcium-dependent movement of troponin I between troponin C and actin as revealed by spin-labeling EPR},
author = {Aihara, Tomoki and Ueki, Shoji and Nakamura, Motoyoshi and Arata, Toshiaki},
abstractNote = {We measured EPR spectra from a spin label on the Cys133 residue of troponin I (TnI) to identify Ca{sup 2+}-induced structural states, based on sensitivity of spin-label mobility to flexibility and tertiary contact of a polypeptide. Spectrum from Tn complexes in the -Ca{sup 2+} state showed that Cys133 was located at a flexible polypeptide segment (rotational correlation time {tau} = 1.9 ns) that was free from TnC. Spectra of both Tn complexes alone and those reconstituted into the thin filaments in the +Ca{sup 2+} state showed that Cys133 existed on a stable segment ({tau} = 4.8 ns) held by TnC. Spectra of reconstituted thin filaments (-Ca{sup 2+} state) revealed that slow mobility ({tau} = 45 ns) was due to tertiary contact of Cys133 with actin, because the same slow mobility was found for TnI-actin and TnI-tropomyosin-actin filaments lacking TnC, T or tropomyosin. We propose that the Cys133 region dissociates from TnC and attaches to the actin surface on the thin filaments, causing muscle relaxation at low Ca{sup 2+} concentrations.},
doi = {10.1016/j.bbrc.2005.12.030},
journal = {Biochemical and Biophysical Research Communications},
number = 2,
volume = 340,
place = {United States},
year = {Fri Feb 10 00:00:00 EST 2006},
month = {Fri Feb 10 00:00:00 EST 2006}
}