期刊
JOURNAL OF MOLECULAR BIOLOGY
卷 414, 期 5, 页码 667-680出版社
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2011.10.026
关键词
force and velocity; actin; mutant; optical tweezers; in vitro motility
资金
- Ministry of Education, Sports, Culture, Science and Technology of Japan
- National Institutes of Health [GM36326, GM93065, HL70041]
- University of Medicine and Dentistry of New Jersey Foundation
- American Heart Association [0850184Z]
- Grants-in-Aid for Scientific Research [21000011, 22227005] Funding Source: KAKEN
To establish et-tropomyosin (Tm)'s structure function relationships in cooperative regulation of muscle contraction, thin filaments were reconstituted with a variety of Tm mutants (Delta 2Tm, Delta 3Tm, Delta 6Tm, P2sTm, P3sTm, P2P3sTm, P1P5Tm, and wtTm), and force and sliding velocity of the thin filament were studied using an in vitro motility assay. In the case of deletion mutants, Delta indicates which of the quasi-equivalent repeats in Tm was deleted. In the case of period (P) mutants, an Ala cluster was introduced into the indicated period to strengthen the Tm-actin interaction. In P1P5Tm, the N-terminal half of period 5 was substituted with that of period 1 to test the quasi-equivalence of these two Tm periods. The reconstitution included bovine cardiac troponin. Deletion studies revealed that period 3 is important for the positive cooperative effect of Tm on actin filament regulation and that period 2 also contributes to this effect at low ionic strength, but to a lesser degree. Furthermore, Tm with one extra Ala cluster at period 2 (P2s) or period 3 (P3s) did not increase force or velocity, whereas Tm with two extra Ala clusters (P2P3s) increased both force and velocity, demonstrating interaction between these periods. Most mutants did not move in the absence of Ca(2+). Notable exceptions were Delta 6Tm and P1P5Tm, which moved near at the full velocity, but with reduced force, which indicate impaired relaxation. These results are consistent with the mechanism that the Tm-actin interaction cooperatively affects actin to result in generation of greater force and velocity. (C) 2011 Elsevier Ltd. All rights reserved.
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