Interaction Of Adenosine Triphosphate Research Articles

How Does Mg2+(aq) Interact with ATP(aq)? Biomolecular Structure through the Lens of Liquid-Jet Photoemission Spectroscopy.

Liquid-jet photoemission spectroscopy (LJ-PES) allows for a direct probing of electronic structure in aqueous solutions. We show the applicability of the approach to biomolecules in a complex environment, exploring site-specific information on the interaction of adenosine triphosphate in the aqueous phase (ATP(aq)) with magnesium (Mg2+(aq)), highlighting the synergy brought about by the simultaneous analysis of different regions in the photoelectron spectrum. In particular, we demonstrate intermolecular Coulombic decay (ICD) spectroscopy as a new and powerful addition to the arsenal of techniques for biomolecular structure investigation. We apply LJ-PES assisted by electronic-structure calculations to study ATP(aq) solutions with and without dissolved Mg2+. Valence photoelectron data reveal spectral changes in the phosphate and adenine features of ATP(aq) due to interactions with the divalent cation. Chemical shifts in Mg 2p, Mg 2s, P 2p, and P 2s core-level spectra as a function of the Mg2+/ATP concentration ratio are correlated to the formation of [Mg(ATP) 2]6-(aq), [MgATP]2-(aq), and [Mg2ATP](aq) complexes, demonstrating the element sensitivity of the technique to Mg2+-phosphate interactions. The most direct probe of the intermolecular interactions between ATP(aq) and Mg2+(aq) is delivered by the emerging ICD electrons following ionization of Mg 1s electrons. ICD spectra are shown to sensitively probe ligand exchange in the Mg2+-ATP(aq) coordination environment. In addition, we report and compare P 2s data from ATP(aq) and adenosine mono- and diphosphate (AMP(aq) and ADP(aq), respectively) solutions, probing the electronic structure of the phosphate chain and the local environment of individual phosphate units in ATP(aq). Our results provide a comprehensive view of the electronic structure of ATP(aq) and Mg2+-ATP(aq) complexes relevant to phosphorylation and dephosphorylation reactions that are central to bioenergetics in living organisms.

ATP-dependent conformational dynamics in a photoactivated adenylate cyclase revealed by fluorescence spectroscopy and small-angle X-ray scattering

Structural insights into the photoactivated adenylate cyclases can be used to develop new ways of controlling cellular cyclic adenosine monophosphate (cAMP) levels for optogenetic and other applications. In this work, we use an integrative approach that combines biophysical and structural biology methods to provide insight on the interaction of adenosine triphosphate (ATP) with the dark-adapted state of the photoactivated adenylate cyclase from the cyanobacterium Oscillatoria acuminata (OaPAC). A moderate affinity of the nucleotide for the enzyme was calculated and the thermodynamic parameters of the interaction have been obtained. Stopped-flow fluorescence spectroscopy and small-angle solution scattering have revealed significant conformational changes in the enzyme, presumably in the adenylate cyclase (AC) domain during the allosteric mechanism of ATP binding to OaPAC with small and large-scale movements observed to the best of our knowledge for the first time in the enzyme in solution upon ATP binding. These results are in line with previously reported drastic conformational changes taking place in several class III AC domains upon nucleotide binding.

Association of adenosine triphosphate with lipid headgroups measured by NMR spectroscopy.

Adenosine triphosphate (ATP) is the energy currency of biological processes because of its central role in energy conversion in biological cells. Given the complexity and the molecular disorder of the cellular environment, the mechanism of energy conversion into useful work still poses challenging questions in molecular biophysics. Using nuclear magnetic resonance spectroscopy and dynamic light scattering, we show that ATP molecules have a measurable affinity to phosphatidylcholine lipid headgroups. The adenosine and ribose groups of the ATP molecule insert into the headgroup region of the membrane as seen by 2D NOESY spectra. Based on 31P NMR measurements, the most likely orientation for the phosphate chain is away from the membrane surface into the water space and the interaction of ATP with lipid headgroups leads to electrostatic charging of membrane surfaces. The interaction of adenosine triphosphate with lipid membranes has relevance to biophysical and biochemical studies of energy conversion in biological cells. In particular, the affinity of ATP to lipid headgroups can affect the interaction with specialized receptors present in biological cells. The observed association of ATP with membrane surfaces primarily through the adenosine group allows phosphate chains to participate in hydrolysis reactions consistent with biochemical data.

Interaction of Adenosine Triphosphate with Phosphatidylcholine Lipid Bilayers

As a polarizable, water soluble molecule, adenosine triphosphate (ATP) can affect the interaction between phosphatidylcholine (PC) lipid bilayers [1, 2]. This is seen by the variation of equilibrium spacings of multilamellar vesicles in ATP solutions that is measured by small-angle x-ray scattering. The most likely scenario is that ATP reduces the van der Waals attraction between PC membranes and at the same time adds an electrostatic repulsion to interbilayer forces by association with lipid headgroups. NMR spectroscopy supports this scenario although it is not yet clear how ATP molecules are distributed at the water-lipid interface. Here we present all-atom molecular dynamics simulations of dilauroyl phosphatidylcholine (DLPC) in the presence of ATP. All-atom simulations containing 100 DLPC lipids and were run in NAMD using the CHARMM force field at 310 K. We present the spatial distribution of ATP molecules as seen in simulations in relation to x-ray and NMR results. [1] Koerner et al, Biophys. J. 2011, [2] Johnson et al., Langmuir 2014.

Regeneration and tolerance factor modulates the effect of adenosine triphosphate–induced interleukin 1β secretion in human macrophages

These studies characterize a molecule known as regeneration and tolerance factor (RTF), which controls inflammation by regulating interleukin 1β (IL-1β) secretion. Recently, it has been demonstrated that the interaction of adenosine triphosphate (ATP) with the P2X7 purinoceptor induces the secretion of IL-1β and initiates the inflammatory response. In these experiments, that the addition of ATP to macrophages was found to induce P2X7 activation and secretion of IL-1β. This secretion is enhanced with anti-RTF antibody in combination with exogenous ATP ( p< 0.005). RTF is also revealed to be able to influence surface ATPase activity and, increase PI incorporation, which is an indicator of P2X7 activation. We demonstrate that RTF has a role in controlling IL-1β secretion by regulating P2X7 activity.

The interaction of adenosinetriphosphate and inorganic phosphate with the sodium pump in red cells.

1. An increase in the intracellular concentration of inorganic phosphate (Pi) reduces the rate of the Na:K exchange catalysed by the Na pump in red cells. The inhibitory effect of Pi is exerted on the maximum rate of flux, Pi having no appreciable effect on the apparent affinity of the Na pump for either internal Na or external K. The effect of Pi is exerted along a rectangular hyperbola which tends to zero as Pi tends to infinity and is half-maximal at about 17 mM internal Pi. 2. Pi does not modify the rate of Na:Na exchange catalysed by the Na pump. 3. A reduction in the intracellular concentration of ATP reduces the maximum rate of Na:K exchange having no effect on the apparent affinity for either internal Na or external K. 4. The effects of ATP and Pi are mutually independent. 5 The lack of effect of ATP and Pi on the apparent affinity for internal Na is compatible with the idea that the affinity of the inner sites of the Na pump remains constant during a pump cycle. 6. The lack of effect of ATP on the apparent affinity for external K and the independence between the effects of ATP and Pi are difficult to explain if the only effect of ATP were its combination at a phosphorylating site. 7. The apparent affinities for K and phosphate become independent of the concentration of ATP, if it is assumed that in our experimental range the phosphorylating site is fully saturated with ATP, the rate of pumping being controlled by the state of occupation of a second non-phosphorylating site whose affinity for ATP is much lower. 8. The lack of effect of Pi on the apparent affinity for external K seems to indicate that during Na:K exchange the conformations of the pump that predominate are endowed with a reactivity towards inorganic phosphate and have the same high affinity for K in both their phospho and their dephospho states. 9. The kinetic behaviour of the Na pump in regard to its interactions with inner and outer cations, ATP and Pi seems to indicate that, in contrast with what happens with soluble allosteric proteins, in the active transport system ligand-induced changes in the reactivity are more important than ligand-induced changes in affinity. In this respect therefore the Na pump behaves as an allosteric 'V system'.

Thermodynamic quantities associated with the interaction of adenosine triphosphate with metal ions.

Thermodynamic quantities associated with the interaction of adenosine triphosphate with metal ions.