Nucleotide binding to sarcoplasmic reticulum vesicles was investigated in the absence of calcium using both filtration and fluorescence measurements. Filtration assays of binding of radioactive nucleotides at concentrations up to 0.1 mM gave a stoichiometry of one ATP-binding site/sarcoplasmic reticulum ATPase molecule. When measured in the presence of calcium under otherwise similar conditions...

P2X receptors are a distinct family of ATP-gated ion channels with a number of physiological roles ranging from smooth muscle contractility to the regulation of blood clotting. In this study we determined whether the UV light-reactive ATP analogues 2-azido ATP, ATP azidoanilide (ATP-AA) and 2',3'-O-(4-benzoylbenzoyl)-ATP (BzATP) can be used to label the ATP binding site of P2X1 receptors. These...

Aminoacyl-tRNA synthetases catalyze the formation of an aminoacyl-AMP from an amino acid and ATP, prior to the aminoacyl transfer to tRNA. A subset of aminoacyl-tRNA synthetases, including glutamyl-tRNA synthetase (GluRS), have a regulation mechanism to avoid aminoacyl-AMP formation in the absence of tRNA. In this study, we determined the crystal structure of the 'non-productive' complex of The...

Human calcium/calmodulin-dependent protein kinase I (CaMKI) plays pivotal roles in the nervous system. The activity of human CaMKI is regulated by a regulatory region including an autoinhibitory segment and a CaM-binding segment. We report here four structures of three CaMKIα truncates in apo form and in complexes with ATP. In an apo, autoinhibited structure, the activation segment adopts a uni...

because of participation in many aspects of human life, and due to oxidation-sensitive characteristics of dopamine (da) and arachidonoyl dopamine (aa-da), the necessity of biocompatible carrier to keep them against oxidation is of importance. in this work, we explored the putative binding sites of da and aa-da to -lactoglobulin (blg) as potent carrier. docking results identified the binding si...

Background: Human epidermal growth factor receptor 2 (Her2) gene located in human chromosome17, encodes Her2 tyrosine kinase protein, and is overexpressed breast cancer cells. activated on phosphorylation of by adenosine triphosphate (ATP). Nonetheless, excessively partakes the development prognosis specific types aggressive cancers. Therefore, inhibition therapy primary target for treatment ca...

Charged, solvent-exposed residues at the entrance to the substrate binding site (gatekeeper residues) produce electrostatic dipole interactions with approaching substrates, and control their access by a novel mechanism called "electrostatic gatekeeper effect". This proof-of-concept study demonstrates that the nucleotide specificity can be engineered by altering the electrostatic properties of t...

This paper presents a study of the role of positive charge in the P(i) binding site of Escherichia coli ATP synthase, the enzyme responsible for ATP-driven proton extrusion and ATP synthesis by oxidative phosphorylation. Arginine residues are known to occur with high propensity in P(i) binding sites of proteins generally and in the P(i) binding site of the betaE catalytic site of ATP synthase s...

Four positively-charged residues, namely betaLys-155, betaArg-182, betaArg-246, and alphaArg-376 have been identified as Pi binding residues in Escherichia coli ATP synthase. They form a triangular Pi binding site in catalytic site betaE where substrate Pi initially binds for ATP synthesis in oxidative phosphorylation. Positive electrostatic charge in the vicinity of betaArg-246 is shown to be ...

We present crystal structures of the calcium-free E2 state of the sarcoplasmic reticulum Ca2+ -ATPase, stabilized by the inhibitor thapsigargin and the ATP analog AMPPCP. The structures allow us to describe the ATP binding site in a modulatory mode uncoupled from the Asp351 phosphorylation site. The Glu439 side chain interacts with AMPPCP via an Mg2+ ion in accordance with previous Fe2+ -cleava...