The Unique Properties of Tonic Smooth Muscle Emerge from Intrinsic as Well as Intermolecular Behaviors of Myosin Molecules
| Autor: | David M. Warshaw, Patty Fagnant, Josh E. Baker, Christine Brosseau |
|---|---|
| Rok vydání: | 2003 |
| Předmět: |
Myosins
Biochemistry Tonic (physiology) Adenosine Triphosphate ATP hydrolysis Myosin medicine Animals Muscle Skeletal Molecular Biology Actin Meromyosin Heavy meromyosin Chemistry Hydrolysis Myosin Subfragments Skeletal muscle Muscle Smooth Cell Biology Actins Recombinant Proteins Biomechanical Phenomena Adenosine Diphosphate Kinetics medicine.anatomical_structure Biophysics ADP binding Chickens Mathematics |
| Zdroj: | Journal of Biological Chemistry. 278:28533-28539 |
| ISSN: | 0021-9258 |
| Popis: | To better understand the molecular basis for some of the unique mechanical properties of tonic smooth muscle, we use a laser trap to assay the mechanochemistry of single smooth muscle heavy meromyosin molecules lacking a seven-amino acid insert in the nucleotide binding loop (minus insert). We measured a second-order ATP-induced actin dissociation rate, kT, of 2.2 x 10(6) m(-1) s(-1), an ADP release rate, k-D, of 19 s(-1), a second-order ADP binding rate, kD, of 60 x 10(5) m(-1) s(-1), and an ADP affinity, KD, of 3.2 microm, which is more than 100-fold greater than that measured for skeletal muscle myosin. By performing in vitro motility studies under nearly identical conditions, we show that the relatively slow actin velocity generated by minus-insert heavy meromyosin is significantly influenced, but not limited, by k-D. Our results support a model in which two separate intermediate steps in the actin-myosin catalyzed ATP hydrolysis reaction are energetically coupled through mechanical interactions, and we discuss this model in the context of the ability of tonic muscle to maintain high forces at low energetic cost (latch). |
| Databáze: | OpenAIRE |
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