T. E. Barman

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2,3-Butanedione monoxime (BDM) reversibly inhibits force production in muscle. At least part of its action appears to be directly on the contractile apparatus. To understand better its mechanism of action, we studied the effect of BDM on the steps of myosin subfragment 1 Mg(2+)-ATPase in 0.1 M potassium acetate, pH 7.4. Because of the rapidity of certain(More)
The kinetics of the tryptophan fluorescence enhancement that occurs when myofibrils (rabbit psoas) are mixed with Mg-ATP were studied by stopped-flow in different solvents (water, 40% ethylene glycol, 20% methanol) at 4 degrees C. Under relaxing conditions (low Ca(2+)) in water (mu = 0.16 M, pH 7.4) and at high ATP concentrations, the transient was(More)
In previous work, we studied the early steps of the Mg(2+)-ATPase activity of Ca(2+)-activated myofibrils [Houadjeto, M., Travers, F., & Barman, T. (1992) Biochemistry 31, 1564-1569]. The myofibrils were free to contract, and the results obtained refer to the ATPase cycle of myofibrils contracting with no external load. Here we studied the ATPase of(More)
Our objective was to determine a good in vitro model for muscle fiber ATPase, and we compared the kinetics of Ca(2+)-activated myofibrils and cross-linked actoS1 in a buffer of physiological ionic strength. The myofibrils were cross-linked chemically to mimic the isometric condition of fibers or were un-cross-linked (the isotonic condition), and temperature(More)
We studied the ATPase of shortening myofibrils at 4 degrees C by the rapid flow quench method. The progress curve has three phases: a P(i) burst, a fast linear phase kF of duration tB, and a deceleration to a slow kS. We propose that kF is the ATPase of myofibrils shortening under zero external load; at tB shortening and ATPase rates are reduced by passive(More)
The myofibril is a good model to study the ATPase of the muscle fibre. When myofibrillar ATPase reaction mixtures are quenched in acid, there is a burst of Pi formation, due to AM.ADP.Pi or Pi, as shown in the scheme: AM+ATP<-->A.M.ATP<-->AM.ADP.Pi<-->AM.ADP+Pi<-->AM+ADP. Therefore, in the steady state, either AM.ADP.Pi or AM.ADP or both predominate. To(More)
Shortening and ATPase rates were measured in Ca2+-activated myofibrils from frog fast muscles in unloaded conditions at 4 degrees C. ATPase rates were determined using the phosphate-binding protein method (free phosphate) and quench flow (total phosphate). Shortening rates at near zero load (V0) were estimated by quenching reaction mixtures 50 ms to 10 s(More)
The inhibitory effect of P3-[1-(2-nitrophenyl)ethyl]adenosine 5'-triphosphate (caged ATP) on the binding of Mg2+-ATP to myofibrils was investigated. The most sensitive method was found to be the monitoring of single turnovers of [gamma-32P] ATP hydrolysis using the quench flow technique. The method was tested using ADP, which was found to have an inhibition(More)
Four-[(1984), J. Biol. Chem. 259, 11908] and six-[(1985) Science 227, 999] state models have been proposed for actomyosin ATPase. A key experiment in deciding between these is whether or not there is a transient Pi burst at high actin. In the first, the cleavage and release of products rates are similar and the Pi burst is low; in the second, there are(More)