Abstract:
:Fluorescence lifetime imaging microscopy is used to demonstrate that different loads applied to a muscle fiber change the microenvironment of the nucleotide binding pocket of myosin. Permeabilized skeletal muscle fibers in rigor were labeled with a fluorescent ATP analog, 3'-DEAC-propylenediamine (pda)-ATP (3'-O-{N-[3-(7-diethylaminocoumarin-3-carboxamido)propyl]carbamoyl}ATP), which was hydrolyzed to the diphosphate. Cycles of small-amplitude stretches and releases (<1% of muscle segment length) were synchronized with fluorescence lifetime imaging and force measurements to correlate the effect of force on the lifetime of the ATP analog bound to the actomyosin complex. Analysis of the fluorescence decay resolved two lifetimes, corresponding to the free nucleotide DEAC-pda-ATP (τ(1) = 0.47 ± 0.03 ns; mean ± SD) and nucleotide bound to the actomyosin complex (τ(2) = 2.21 ± 0.06 ns at low strain). Whereas τ(1) did not change with force, τ(2) showed a linear dependence with the force applied to the muscle of 0.43 ± 0.05 ps/kPa. Hence, the molecular environment of the nucleotide binding pocket of myosin is directly affected by a change of length applied at the ends of the fiber segments. These changes may help explain how force modulates the actomyosin ATPase cycle and thus the physiology and energetics of contraction.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Ibanez-Garcia D,Requejo-Isidro J,Webb MR,West TG,French P,Ferenczi MAdoi
10.1016/j.bpj.2010.07.052subject
Has Abstractpub_date
2010-10-06 00:00:00pages
2163-9issue
7eissn
0006-3495issn
1542-0086pii
S0006-3495(10)00924-0journal_volume
99pub_type
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