Orientation of the essential light chain region of myosin in relaxed, active, and rigor muscle.
The orientation of the ELC region of myosin in skeletal muscle was determined by polarized fluorescence from ELC mutants in which pairs of introduced cysteines were cross-linked by BSR. The purified ELC-BSRs were exchanged for native ELC in demembranated fibers from rabbit psoas muscle using a trifluoperazine-based protocol that preserved fiber function. In the absence of MgATP (in rigor) the ELC orientation distribution was narrow; in terms of crystallographic structures of the myosin head, the LCD long axis linking heavy-chain residues 707 and 843 makes an angle (beta) of 120-125 degrees with the filament axis. This is approximately 30 degrees larger than the broader distribution determined previously from RLC probes, suggesting that, relative to crystallographic structures, the LCD is bent between its ELC and RLC regions in rigor muscle. The ELC orientation distribution in relaxed muscle had two broad peaks with beta approximately 70 degrees and approximately 110 degrees, which may correspond to the two head regions of each myosin molecule, in contrast with the single broad distribution of the RLC region in relaxed muscle. During isometric contraction the ELC orientation distribution peaked at beta approximately 105 degrees , similar to that determined previously for the RLC region.
Knowles
Andrea C
AC
Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom.
Ferguson
Roisean E
RE
Brandmeier
Birgit D
BD
Sun
Yin-Biao
YB
Trentham
David R
DR
Irving
Malcolm
M
D000818:Animals; D002645:Chickens; D003432:Cross-Linking Reagents / Q000494:pharmacology; D018613:Microscopy, Confocal; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism; D009127:Muscle Rigidity / Q000378:metabolism*; D009132:Muscles / Q000187:drug effects / Q000378:metabolism*; D018994:Myosin Light Chains / Q000737:chemistry*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011817:Rabbits
D003432:Cross-Linking Reagents; D018994:Myosin Light Chains