Observations with acetylcholinesterase can be well explained by postulating that the active site contains two subsites: one, an anionic site which binds and orients substituted ammonium ions, and the other, an esteratic site where the hydrolytic process occurs and which contains a basic group which is acetylated and deacetylated during the process (4, 5). The formation of an acetyl enzyme sugge...

Kinesin advances 8 nm along a microtubule per ATP hydrolyzed, but the mechanism responsible for coordinating the enzymatic cycles of kinesin's two identical motor domains remains unresolved. Here, we have tested whether such coordination is mediated by intramolecular tension generated by the "neck linkers," mechanical elements that span between the motor domains. When tension is reduced by exte...

F(1)-ATPase catalyses ATP hydrolysis and converts the cellular chemical energy into mechanical rotation. The hydrolysis reaction in F(1)-ATPase does not follow the widely believed Michaelis-Menten mechanism. Instead, the hydrolysis mechanism behaves in an ATP-dependent manner. We develop a model for enzyme kinetics and hydrolysis cooperativity of F(1)-ATPase which involves the binding-state cha...

The activation of molecular chaperone heat-shock protein 90 (Hsp90) is dependent on ATP binding and hydrolysis, which occurs in the N-terminal domains of protein. Here, we have determined three crystal structures of the N-terminal domain of human Hsp90 in native and in complex with ATP and ATP analog, providing a clear view of the catalytic mechanism of ATP hydrolysis by Hsp90. Additionally, th...

Evidence is presented that caffeine does not act on the mitochondrial Ca uptake system and that its effect cannot be attributed to the accumulation of adenosine 3',5'-phosphate. Two distinct caffeine effects are described. At high ATP concentrations caffeine decreases the coupling between ATP hydrolysis and Ca inflow. It either inhibits inflow without any inhibition of the rate of ATP hydrolysi...

Cross-linking studies on the Escherichia coli F0F1-ATP synthase indicated a site of interaction involving gamma and epsilon subunits in F1 and subunit c in F0 (Watts, S. D., Tang, C., and Capaldi, R. A. (1996) J. Biol. Chem. 271, 28341-28347). To assess the function of these interactions, we introduced random mutations in this region of the gamma subunit (gamma194-213). One mutation, gammaGlu-2...

new biodegradable network polymers containing siloxane-linked polymeric prodrugs of 5-ammino-2-hydroxybenzoic acid (5-asa) in the main chain were prepared by ter polymerization of methacrylic acid (ma), 2-hydroxyethylmethacrylate (hema), and bis (trimethylsilyloxy) methylsilane (vbm) in the presence of some new cross-linking agents.the monomers and polymers were characterized by ft-ir and 1h-nm...

F1-ATPase (F1) is a reversible ATP-driven rotary motor protein. When its rotary shaft is reversely rotated, F1 produces ATP against the chemical potential of ATP hydrolysis, suggesting that F1 modulates the rate constants and equilibriums of catalytic reaction steps depending on the rotary angle of the shaft. Although the chemomechanical coupling scheme of F1 has been determined, it is unclear ...

Background: Cyclic aminals are core features of natural products, drug molecules and important synthetic intermediates. Despite their relevance, systematic investigations into their stability towards hydrolysis depending on the pH value are lacking. Results: A set of cyclic aminals was synthesized and their stability quantified by kinetic measurements. Steric and electronic effects were investi...

................................................................................................................................ 3 Introduction ........................................................................................................................... 6 1 Theoretical Background .................................................................................................. 7 1...