Orientation of Paramagnetic Probes Attached to Gizzard Regulatory Light Chain Bound to Myosin Heads in Rabbit Skeletal Muscle
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- 作者：Liang Zhao ; Jeremy Gollub ; and Roger Cooke
- 刊名：Biochemistry
- 出版年：1996
- 出版时间：August 6, 1996
- 年：1996
- 卷：35
- 期：31
- 页码：10158 - 10165
- 全文大小：378K
- 年卷期：v.35,no.31(August 6, 1996)
- ISSN：1520-4995
文摘
The orientation of the myosin neck was monitored using electronparamagnetic resonance(EPR) spectroscopy. Gizzard regulatory light chain was labeledwith a nitroxide spin probe and exchangedfor the native subunit, located in the myosin neck, in rabbit psoasmuscle fibers. The EPR spectra ofrigor fibers indicated a substantial degree of probe immobilization andshowed a strong dependence onthe orientation of the fiber axis relative to the magnetic field,indicating that the neck was ordered in thisstate. Spectra of relaxed fibers at 24 
C showed that the neckwas disordered, but the spectra of relaxedfibers at 4 C indicated that the neck was partially ordered.Active fibers at the two temperatures producedspectra identical to relaxed fibers, indicating that no novel anglescould be seen in the neck during thepowerstroke. Proteolytic fragments of myosin, S1 and HMM, wereexchanged with labeled light chainsand bound to thin filaments in unlabeled fibers. The distributionof probe orientations for HMM wasidentical to that of labeled rigor fibers, while S1 showed a slightlydifferent distribution, suggesting thatthe neck is distorted (by a few degrees) by the interactions of the twoheads of myosin when bound toactin.
C showed that the neckwas disordered, but the spectra of relaxedfibers at 4 C indicated that the neck was partially ordered.Active fibers at the two temperatures producedspectra identical to relaxed fibers, indicating that no novel anglescould be seen in the neck during thepowerstroke. Proteolytic fragments of myosin, S1 and HMM, wereexchanged with labeled light chainsand bound to thin filaments in unlabeled fibers. The distributionof probe orientations for HMM wasidentical to that of labeled rigor fibers, while S1 showed a slightlydifferent distribution, suggesting thatthe neck is distorted (by a few degrees) by the interactions of the twoheads of myosin when bound toactin.