Smooth muscle myosin phosphorylated at single head shows sustained mechanical activity
Graduate School of Biomedical Sciences; Department of Physiology
Life Sciences | Medicine and Health Sciences
Smooth muscle contraction is regulated by the phosphorylation of myosin. It is well known that tonic smooth muscles can maintain force with low energy consumption (latch state); however, the molecular mechanism underlying this phenomenon is unresolved. Here we show that single-head phosphorylated smooth myosin (SHPMII) exhibits fast ( approximately 24 s(-1)) and slow prolonged ( approximately 1 s(-1)) actin interactions, whereas double-head phosphorylated myosin (DHPMII) predominantly exhibits the fast ( approximately 29 s(-1)) interaction, suggesting that the phosphorylated head of SHPMII is mechanically as active as that of DHPMII. Both the fast and the slow actin interactions of SHPMII support the positive net mechanical displacement of actin. The actin translocating velocity of SHPMII was much slower than that of DHPMII, which is consistent with the slow actin interaction of SHPMII. We propose that the "latch state" can be explained by the motor characteristics of SHPMII that is present during the sustained phase of contraction.
DOI of Published Version
J Biol Chem. 2008 Jun 6;283(23):15611-8. Epub 2008 Apr 11. Link to article on publisher's site
The Journal of biological chemistry
Tanaka, Hiroto; Homma, Kazuaki; White, Howard D.; Yanagida, Toshio; and Ikebe, Mitsuo, "Smooth muscle myosin phosphorylated at single head shows sustained mechanical activity" (2008). GSBS Student Publications. 1477.