Trimethylamine N-oxide suppresses the activity of the actomyosin motor.
BACKGROUND
During actomyosin interactions, the transduction of energy from ATP hydrolysis to motility seems to occur with the modulation of hydration. Trimethylamine N-oxide (TMAO) perturbs the surface of proteins by altering hydrogen bonding in a manner opposite to that of urea. Hence, we focus on the effects of TMAO on the motility and ATPase activation of actomyosin complexes.


METHODS
Actin and heavy meromyosin (HMM) were prepared from rabbit skeletal muscle. Structural changes in HMM were detected using fluorescence and circular dichroism spectroscopy. The sliding velocity of rhodamine-phalloidin-bound actin filaments on HMM was measured using an in vitro motility assay. ATPase activity was measured using a malachite green method.


RESULTS
Although TMAO, unlike urea, stabilized the HMM structure, both the sliding velocity and ATPase activity of acto-HMM were considerably decreased with increasing TMAO concentrations from 0-1.0M. Whereas urea-induced decreases in the structural stability of HMM were recovered by TMAO, TMAO further decreased the urea-induced decrease in ATPase activation. Urea and TMAO were found to have counteractive effects on motility at concentrations of 0.6M and 0.2M, respectively.


CONCLUSIONS
The excessive stabilization of the HMM structure by TMAO may suppress its activities; however, the counteractive effects of urea and TMAO on actomyosin motor activity is distinct from their effects on HMM stability.


CONCLUSIONS
The present results provide insight into not only the water-related properties of proteins, but also the physiological significance of TMAO and urea osmolytes in the muscular proteins of water-stressed animals.
Deprtment of Bio-Systems Engineering, Graduate School of Science and Engineering, Yamagata University, Yonezawa 992-8510, Japan.
Ryusei
R
Kumemoto
Kento
K
Yusa
Tomohiro
T
Shibayama
Kuniyuki
K
Hatori
D008841:Actin Cytoskeleton / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D000205:Actomyosin / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D066298:In Vitro Techniques; D008744:Methylamines / Q000494:pharmacology*; D009068:Movement / Q000187:drug effects*; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D015879:Myosin Subfragments / Q000737:chemistry / Q000378:metabolism; D009994:Osmolar Concentration; D055550:Protein Stability / Q000187:drug effects; D011817:Rabbits; D014508:Urea / Q000494:pharmacology
D008744:Methylamines; D046912:Multiprotein Complexes; D015879:Myosin Subfragments; D014508:Urea; D000205:Actomyosin; D000251:Adenosine Triphosphatases; C005855:trimethyloxamine