Myosin Surface Loop 4 Modulates Inhibition of Actomyosin 1b Atpase Activity by Tropomyosin.
From: Boston Biomedical Research Institute, 64 Grove Street, Watertown, Massachusetts 02472, USA.
Biochemistry
- Publish Date: Mar 2007
- ISSN: 0006-2960
- Volume: 46
- Issue: 10
- Pages: 2779-86
- Medium: Print
- Language: English
- Citation (JAMA): Lieto-Trivedi Alena, Dash Sheffali, Coluccio Lynne M, et al. Myosin Surface Loop 4 Modulates Inhibition of Actomyosin 1b Atpase Activity by Tropomyosin.. Biochemistry Mar 2007;46:2779-86
Abstract
Structural studies of the class I myosin, MyoE, led to the predictions that loop 4, a surface loop near the actin-binding region that is longer in class I myosins than in other myosin subclasses, might limit binding of myosins I to actin when actin-binding proteins, like tropomyosin, are present, and might account for the exclusion of myosin I from stress fibers. To test these hypotheses, mutant molecules of the related mammalian class I myosin, Myo1b, in which loop 4 was truncated (from an amino acid sequence of RMNGLDES to NGLD) or replaced with the shorter and distinct loop 4 found in Dictyostelium myosin II (GAGEGA), were expressed in vitro and their interaction with actin and with actin-tropomyosin was tested. Saturating amounts of expressed fibroblast tropomyosin-2 resulted in a decrease in the maximum actin-activated Mg2+-ATPase activity of wild-type Myo1b but had little or no effect on the actin-activated Mg2+-ATPase activity of the two mutants. In motility assays, few actin filaments bound tightly to Myo1b-WT-coated cover slips when tropomyosin-2 was present, whereas actin filaments both bound and were translocated by Myo1b-NGLD or Myo1b-GAGEGA in both the presence and absence of tropomyosin-2. When expressed in mammalian cells, like the wild type, the mutant myosins were largely excluded from tropomyosin-containing actin filaments, indicating that in the cell additional factors besides loop 4 determine targeting of myosins I to specific subpopulations of actin filaments.
Mesh Headings (Keywords): Actomyosin, Adenosine Triphosphatases, Amino Acid Sequence, Animals, Hela Cells, Humans, Models, Molecular, Molecular Sequence Data, Mutation, Myosins, Rabbits, Tropomyosin
Check for Full Text / PubMed Unique Identifier (PMID): 17298083
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