Resonance energy transfer evidence for two attached states of the actomyosin complex.

D G Bhandari, H R Trayer, I P Trayer

FEBS letters 1985 Jul 22

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Resonance energy transfer measurements were made between a donor fluorophore, N-(bromacetyl)-N'-(1-sulpho-5-naphthyl)ethylenediamine, located on the single cysteine of the Al light chain of myosin (S1(A1), and an acceptor fluorophore, 5-(iodoacetamido)fluorescein, sited on Cys-374 of actin. In the binary rigor complex a transfer efficiency of 24% was noted, representing a spatial separation of about 6 nm. When the same measurements were made using a stable analogue of S1 X ATP, in which the fast reacting SH1 thiol group is crosslinked to another thiol group in the 20 kDa domain of S1, the 2 fluorophores were found to have moved closer together by greater than or equal to 3 nm. This provides, for the first time, direct experimental evidence for a change in structure of the myosin crossbridge that could account for tension generation.

Citation

D G Bhandari, H R Trayer, I P Trayer. Resonance energy transfer evidence for two attached states of the actomyosin complex. FEBS letters. 1985 Jul 22;187(1):160-6