Plant and Cell Physiology Advance Access originally published online on October 4, 2007
Plant and Cell Physiology 2007 48(11):1558-1566; doi:10.1093/pcp/pcm126
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Binding of Chara Myosin Globular Tail Domain to Phospholipid Vesicles
1Department of Biology, Chiba University, Yayoicho, Inage-ku, Chiba, 263-8522 Japan
2Department of Pharmacology, Juntendo University, Medical School, Hongo, Bunkyo-ku, Tokyo, 113-8500 Japan
*Corresponding author: E-mail, yamamoto{at}bio.s.chiba-u.ac.jp; Fax, +81-43-290-2809.
| Abstract |
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Binding of Chara myosin globular tail domain to phospholipid vesicles was investigated quantitatively. It was found that the globular tail domain binds to vesicles made from acidic phospholipids but not to those made from neutral phospholipids. This binding was weakened at high KCl concentration, suggesting that the binding is electrostatic by nature. The dissociation constant for the binding of the globular tail domain to 20% phosphatidylserine vesicles (similar to endoplasmic reticulum in acidic phospholipid contents) at 150 mM KCl was 273 nM. The free energy change due to this binding calculated from the dissociation constant was –37.3 kJ mol–1. Thus the bond between the globular tail domain and membrane phospholipids would not be broken when the motor domain of Chara myosin moves along the actin filament using the energy of ATP hydrolysis (
G°' = –30.5 kJ mol–1). Our results suggested that direct binding of Chara myosin to the endoplasmic reticulum membrane through the globular tail domain could work satisfactorily in Chara cytoplasmic streaming. We also suggest a possible regulatory mechanism of cytoplasmic streaming including phosphorylation-dependent dissociation of the globular tail domain from the endoplasmic reticulum membrane.
Keywords: Ca2+ regulation - Chara corallina - Cytoplasmic streaming - Globular tail domain - Plant myosin - Phospholipid binding
Abbreviations:
BSA, bovine serum albumin; DTT, dithiothreitol; ER, endoplasmic reticulum; GST, glutathione S-transferase; GTD, globular tail domain; PC, phosphatidylcholine; PE, phosphatidylethanolamine; PI, phosphatidylinositol; PIP2, phosphatidylinositol 4,5-bisphosphate; PMSF, phenylmethylsulfonyl fluoride; PS, phosphatidylserine; TAME, N
-p-tosyl-L-arginine methyl ester hydrochloride; TPCK, N-p-tosyl-L-phenylalanine chloromethylketone.
(Received July 20, 2007; Accepted September 26, 2007)
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