Journal Article

Enzymatic Activity and Motility of Recombinant <i>Arabidopsis</i> Myosin XI, MYA1

You Hachikubo, Kohji Ito, John Schiefelbein, Dietmar J. Manstein and Keiichi Yamamoto

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 48, issue 6, pages 886-891
Published in print June 2007 | ISSN: 0032-0781
Published online June 2007 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcm054
Enzymatic Activity and Motility of Recombinant Arabidopsis Myosin XI, MYA1

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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We expressed recombinant Arabidopsis myosin XI (MYA1), in which the motor domain of MYA1 was connected to an artificial lever arm composed of triple helical repeats of Dictyostelium α-actinin, in order to understand its motor activity and intracellular function. The Vmax and Kactin of the actin-activated Mg2+ ATPase activity of the recombinant MYA1 were 50.7 Pi head−1 s−1 and 30.2 μM, respectively, at 25°C. The recombinant MYA1 could translocate actin filament at the maximum velocity of 1.8 μm s−1 at 25°C in the in vitro motility assay. The value corresponded to a motility of 3.2 μm s−1 for native MYA1 if we consider the difference in the lever arm length, and this value was very close to the velocity of cytoplasmic streaming in Arabidopsis hypocotyl epidermal cells. The extent of inhibition by ADP of the motility of MYA1 was similar to that of the well-known processive motor, myosin V, suggesting that MYA1 is a processive motor. The dissociation rate of the actin–MYA1-ADP complex induced by ATP (73.5 s−1) and the Vmax value of the actin-activated Mg2+ ATPase activity revealed that MYA1 stays in the actin-bound state for about 70% of its mechanochemical cycle time. This high ratio of actin-bound states is also a characteristic of processive motors. Our results strongly suggest that MYA1 is a processive motor and involved in vesicle transport and/or cytoplasmic streaming.

Keywords: Arabidopsis; ATPase; Motility; MYA1; Myosin; Processivity

Journal Article.  4224 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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