Biomaterial Database

Intermediate oxygen exchange catalyzed by the actin-activated skeletal myosin adenosinetriphosphatase. 1989

J A Evans, and E Eisenberg

Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, Bethesda, Maryland 20892.

Considerable effort has been devoted to understanding the mechanism of 18O exchange in skinned skeletal and insect muscle fibers. However, a full understanding of the mechanism of 18O exchange in muscle fibers requires an understanding of the mechanism of 18O exchange in the simpler in vitro systems employing myosin subfragment 1 (S-1) and heavy meromyosin (HMM). In the present study, using both S-1 and S-1 covalently cross-linked to actin, we show first that over a wide range of temperature, ionic strength, and actin concentration there is only one pathway of 18O exchange with S-1. This is also the case with HMM except at very low ionic strength and low actin concentration, and even here, the data can be explained if 20% of the HMM is denatured in such a way that it shows no 18O exchange. Our results also show that actin markedly decreases the rate of 18O exchange. If it is assumed that Pi release is rate limiting, the four-state kinetic model of the actomyosin ATPase cannot fit these 18O exchange data. However, if it is assumed that the ATP hydrolysis step is rate limiting and Pi release is very fast, the four-state kinetic model can qualitatively fit these data although the fit is not perfect. A better fit to the 18O exchange data can be obtained with the six-state kinetic model of the actomyosin ATPase, but this fit requires the assumption that, at saturating actin concentration, the rate of Pi rotation is about 9-fold slower than the rate of reversal of the ATP hydrolysis step.

UI	MeSH Term	Description	Entries
D007527	Isoenzymes	Structurally related forms of an enzyme. Each isoenzyme has the same mechanism and classification, but differs in its chemical, physical, or immunological characteristics.	Alloenzyme,Allozyme,Isoenzyme,Isozyme,Isozymes,Alloenzymes,Allozymes
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008956	Models, Chemical	Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.	Chemical Models,Chemical Model,Model, Chemical
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D009218	Myosins	A diverse superfamily of proteins that function as translocating proteins. They share the common characteristics of being able to bind ACTINS and hydrolyze MgATP. Myosins generally consist of heavy chains which are involved in locomotion, and light chains which are involved in regulation. Within the structure of myosin heavy chain are three domains: the head, the neck and the tail. The head region of the heavy chain contains the actin binding domain and MgATPase domain which provides energy for locomotion. The neck region is involved in binding the light-chains. The tail region provides the anchoring point that maintains the position of the heavy chain. The superfamily of myosins is organized into structural classes based upon the type and arrangement of the subunits they contain.	Myosin ATPase,ATPase, Actin-Activated,ATPase, Actomyosin,ATPase, Myosin,Actin-Activated ATPase,Actomyosin ATPase,Actomyosin Adenosinetriphosphatase,Adenosine Triphosphatase, Myosin,Adenosinetriphosphatase, Actomyosin,Adenosinetriphosphatase, Myosin,Myosin,Myosin Adenosinetriphosphatase,ATPase, Actin Activated,Actin Activated ATPase,Myosin Adenosine Triphosphatase
D009994	Osmolar Concentration	The concentration of osmotically active particles in solution expressed in terms of osmoles of solute per liter of solution. Osmolality is expressed in terms of osmoles of solute per kilogram of solvent.	Ionic Strength,Osmolality,Osmolarity,Concentration, Osmolar,Concentrations, Osmolar,Ionic Strengths,Osmolalities,Osmolar Concentrations,Osmolarities,Strength, Ionic,Strengths, Ionic
D010100	Oxygen	An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration.	Dioxygen,Oxygen-16,Oxygen 16
D010446	Peptide Fragments	Partial proteins formed by partial hydrolysis of complete proteins or generated through PROTEIN ENGINEERING techniques.	Peptide Fragment,Fragment, Peptide,Fragments, Peptide
D003432	Cross-Linking Reagents	Reagents with two reactive groups, usually at opposite ends of the molecule, that are capable of reacting with and thereby forming bridges between side chains of amino acids in proteins; the locations of naturally reactive areas within proteins can thereby be identified; may also be used for other macromolecules, like glycoproteins, nucleic acids, or other.	Bifunctional Reagent,Bifunctional Reagents,Cross Linking Reagent,Crosslinking Reagent,Cross Linking Reagents,Crosslinking Reagents,Linking Reagent, Cross,Linking Reagents, Cross,Reagent, Bifunctional,Reagent, Cross Linking,Reagent, Crosslinking,Reagents, Bifunctional,Reagents, Cross Linking,Reagents, Cross-Linking,Reagents, Crosslinking
D006868	Hydrolysis	The process of cleaving a chemical compound by the addition of a molecule of water.