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

Abstract

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.