Journal article
A novel electron paramagnetic resonance spin label and its application to study the cross-bridge cycle
Biophysical journal, Vol.68(4 Suppl), pp.128S-134S
04/01/1995
PMCID: PMC1281893
PMID: 7787055
Abstract
We have used a novel alpha-iodoketone spin-label (IKSL) to study myosin head orientation and cross-bridge dynamics in the putative pre-powerstroke state. Possible perturbation of the cross-bridge cycle by the label was assayed by the sinusoidal analysis method (Kawai and Brandt, 1980; Kawai and Zhao, 1993), which determines the rate constants of the elementary steps in the cycle. A comparison of the rates obtained from unlabeled and IKSL fibers revealed small (10-20%) changes in the ATP hydrolysis rate and in the rate constants of the elementary steps. The labeling induced small changes (< 13%) in the distribution of the cross-bridges among the various intermediate states. Pre-powerstroke cross-bridges were induced by aluminum fluoride in the presence of Ca2+ and ATP. In this state, force development is inhibited, but a large proportion (40%) of the cross-bridges are still attached to the thin filament. We have used conventional electron paramagnetic resonance to measure orientation, and have found that the pre-powerstroke heads are as disordered as in relaxation. Their mobility, as determined by saturation transfer electron paramagnetic resonance, was significantly restricted. Assuming that stiffness is proportional to the fraction of strongly attached heads, the rotational correlation time of the bound heads is estimated to be tau r = approximately 150-400 microseconds.
Details
- Title: Subtitle
- A novel electron paramagnetic resonance spin label and its application to study the cross-bridge cycle
- Creators
- D Raucher - Institute of Molecular Biophysics, Florida State University, Tallahassee 32306, USAE A Fajer - Institute of Molecular Biophysics, Florida State University, Tallahassee 32306, USAC Sár - Institute of Molecular Biophysics, Florida State University, Tallahassee 32306, USAK Hideg - Institute of Molecular Biophysics, Florida State University, Tallahassee 32306, USAY Zhao - Institute of Molecular Biophysics, Florida State University, Tallahassee 32306, USAM Kawai - Institute of Molecular Biophysics, Florida State University, Tallahassee 32306, USAP G Fajer - Institute of Molecular Biophysics, Florida State University, Tallahassee 32306, USA
- Resource Type
- Journal article
- Publication Details
- Biophysical journal, Vol.68(4 Suppl), pp.128S-134S
- PMID
- 7787055
- PMCID
- PMC1281893
- ISSN
- 0006-3495
- eISSN
- 1542-0086
- Language
- English
- Date published
- 04/01/1995
- Academic Unit
- Anatomy and Cell Biology; Internal Medicine
- Record Identifier
- 9984284452402771
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