GSBS Student Publications

Title

Dual regulation of mammalian myosin VI motor function

UMMS Affiliation

Graduate School of Biomedical Sciences; Department of Physiology

Date

8-23-2001

Document Type

Article

Medical Subject Headings

Actins; Adenosine Triphosphatases; Adenosine Triphosphate; Animals; Calcium; Calmodulin; Mice; Microfilaments; Models, Molecular; Molecular Motor Proteins; Myosin Heavy Chains; Phosphorylation; Protein Binding; Protein-Serine-Threonine Kinases; Recombinant Proteins; Threonine; p21-Activated Kinases

Disciplines

Life Sciences | Medicine and Health Sciences

Abstract

Myosin VI is expressed in a variety of cell types and is thought to play a role in membrane trafficking and endocytosis, yet its motor function and regulation are not understood. The present study clarified mammalian myosin VI motor function and regulation at a molecular level. Myosin VI ATPase activity was highly activated by actin with K(actin) of 9 microm. A predominant amount of myosin VI bound to actin in the presence of ATP unlike conventional myosins. K(ATP) was much higher than those of other known myosins, suggesting that myosin VI has a weak affinity or slow binding for ATP. On the other hand, ADP markedly inhibited the actin-activated ATPase activity, suggesting a high affinity for ADP. These results suggested that myosin VI is predominantly in a strong actin binding state during the ATPase cycle. p21-activated kinase 3 phosphorylated myosin VI, and the site was identified as Thr(406). The phosphorylation of myosin VI significantly facilitated the actin-translocating activity of myosin VI. On the other hand, Ca(2+) diminished the actin-translocating activity of myosin VI although the actin-activated ATPase activity was not affected by Ca(2+). Calmodulin was not dissociated from the heavy chain at high Ca(2+), suggesting that a conformational change of calmodulin upon Ca(2+) binding, but not its physical dissociation, determines the inhibition of the motility activity. The present results revealed the dual regulation of myosin VI by phosphorylation and Ca(2+) binding to calmodulin light chain.

Rights and Permissions

Citation: J Biol Chem. 2001 Oct 26;276(43):39600-7. Epub 2001 Aug 21. Link to article on publisher's site

DOI of Published Version

10.1074/jbc.M105080200

Related Resources

Link to Article in PubMed

Journal Title

The Journal of biological chemistry

PubMed ID

11517222