GTPγS-dependent regulation of smooth muscle contractile elements

Y. Kubota, M. Nomura, K. E. Kamm, M. C. Mumby, J. T. Stull

Research output: Contribution to journalArticlepeer-review

110 Scopus citations


Guanosine 5'-O-(3-thiotriphosphate) (GTPγS) increases the sensitivity of the contractile response to activation by Ca2+ in permeabilized tracheal smooth muscle. Increased tension was associated with a proportional increase in myosin light chain phosphorylation. The site of phosphorylation was determined to be serine-19, which corresponds to the site rapidly phosphorylated by myosin light chain kinase. GTPγS did not affect the contraction induced by the protein phosphatase inhibitor okadaic acid but did enhance contraction produced by Ca2+-independent myosin light chain kinase. In tracheal homogenates Ca2+-dependent myosin light chain kinase activity was not affected by GTPγS; however, dephosphorylation of 32P-labeled heavy meromyosin by phosphatase was inhibited. Thus GTPγS may increase the Ca2+ sensitivity of contractile elements in tracheal smooth muscle by inhibition of protein phosphatase activity toward myosin light chain.

Original languageEnglish (US)
Pages (from-to)C405-C410
JournalAmerican Journal of Physiology - Cell Physiology
Issue number2 31-2
StatePublished - 1992


  • calcium sensitivity
  • myosin light chain kinase
  • myosin phosphorylation
  • protein phosphatase

ASJC Scopus subject areas

  • Physiology
  • Cell Biology


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