Orientation of the essential light chain region of myosin in relaxed, active, and rigor muscle

Andrea C. Knowles, Roisean E. Ferguson, Birgit D. Brandmeier, Yin-Biao Sun, David R. Trentham, Malcolm Irving

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)

Abstract

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. lament axis. This is similar to 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 similar to 70 degrees and similar to 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 similar to 105 degrees, similar to that determined previously for the RLC region.
Original languageEnglish
Pages (from-to)3882 - 3891
Number of pages10
JournalBiophysical Journal
Volume95
Issue number8
DOIs
Publication statusPublished - 15 Oct 2008

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