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W o r l d C o n g r e s s o n
Materials Science & Engineering
Nano Research & Applications
ISSN: 2471-9838
August 23-25, 2018
Amsterdam, Netherlands
Materials Congress 2018
Page 21
A
lthough more than 50 years have passed since the discovery of the sliding
filament mechanism in muscle contraction, molecular mechanism of myosin
head power and recovery strokes still remains to be a mystery. Using the gas
environmental chamber (EC) attached to the transmission electron microscope,
we have succeeded in visualizing and recording myosin head power and recovery
strokes in individual myosin heads, coupled with ATP hydrolysis. The results
hitherto obtained are summarized as follows: (1) In the absence of actin filaments
and ATP, myosin heads fluctuate around a definite neutral position, so that
time-averaged myosin head position remains unchanged with time; (2) On ATP
application, myosin heads move away from, but not towards, the bare region at
the center of myosin filaments, indicating myosin heads perform recovery stroke;
(3) The average amplitude of the recovery stroke is ~6 nm; (4) In the presence of
actin filaments, myosin heads perform power stroke by stretching adjacent elastic
structure due to a limited amount of ATP applied; (5) The average amplitude of
power stroke is 3.3 nm at the distal region, and 2.5 nm at the proximal region of
myosin head catalytic domain; (6) In both power and recovery strokes, myosin
heads return to their neutral position after complete exhaustion of ATP applied,
indicating that myosin heads (M) can take three definite positions, i.e., neutral,
post-power stroke, and post recovery stroke positions, the transition between
them is associated with reaction, M-ATP → M-ADP-Pi. We emphasize that our EC
experiments are extremely promising, if coupled with the methods of laser flash
photolysis of caged ATP and time-resolved electron microscopy.
Biography
Haruo Sugi has completed his PhD from the University of
Tokyo in 1962, and worked in the University of Tokyo, Columbia
University and National Institutes of Health. He was Professor
and Chairman in the Department of Physiology, School of
Medicine, Teikyo University from 1973 to 2004 and when
he became Emeritus Professor, from 1998 to 2008, he was
Chairman of Muscle Committee in the International Union of
Physiological Sciences (IUPS).
sugi@kyf.biglobe.ne.jpBasic properties of myosin head power and
recovery strokes as revealed by experiments
using the gas environmental chamber
Haruo Sugi
Teikyo University, Japan
Haruo Sugi, Nano Res Appl 2018, Volume: 4
DOI: 10.21767/2471-9838-C4-016