期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 106, 期 51, 页码 21585-21590出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0910787106
关键词
actin; ATPase; motility; cytoplasmic streaming; molecular engineering
资金
- Ministry of Science, Culture and Education of Japan
- Grants-in-Aid for Scientific Research [21570159] Funding Source: KAKEN
Most myosins have a positively charged loop 2 with a cluster of lysine residues that bind to the negatively charged N-terminal segment of actin. However, the net charge of loop 2 of very fast Chara myosin is zero and there is no lysine cluster in it. In contrast, Chara myosin has a highly positively charged loop 3. To elucidate the role of these unique surface loops of Chara myosin in its high velocity and high actin-activated ATPase activity, we have undertaken mutational analysis using recombinant Chara myosin motor domain. It was found that net positive charge in loop 3 affected V-max and K-app of actin activated ATPase activity, while it affected the velocity only slightly. The net positive charge in loop 2 affected K-app and the velocity, although it did not affect V-max. Our results suggested that Chara myosin has evolved to have highly positively charged loop 3 for its high ATPase activity and have less positively charged loop 2 for its high velocity. Since high positive charge in loop 3 and low positive charge in loop 2 seem to be one of the reasons for Chara myosin's high velocity, we manipulated charge contents in loops 2 and 3 of Dictyostelium myosin (class II). Removing positive charge from loop 2 and adding positive charge to loop 3 of Dictyostelium myosin made its velocity higher than that of the wild type, suggesting that the charge strategy in loops 2 and 3 is widely applicable.
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